Abstract:

A mirror device comprises: a plurality of electrodes disposed on a
substrate; a hinge connected to at least one of the electrodes; a mirror
connected to the hinge and corresponding to at least one of the
electrodes, wherein a barrier layer is comprised between the hinge and
mirror, and/or between the hinge and electrode. Also noted is a mirror
device production method for producing such-configured mirror device.
Further noted is a projection apparatus comprising such-configured mirror
device.

Claims:

1. A mirror device, comprising:a plurality of electrodes disposed on a
substrate;a hinge connected to at least one of the electrodes and the
hinge stands on said substrate extending along substantially a vertical
direction from the substrate; andsaid hinge support a mirror disposed on
top of said hinge along substantially a horizontal direction wherein a
cross sectional area of said hinge near the electrode is less than or
equal to a cross sectional area of said hinge near said mirror.

2. A mirror device, comprising:a plurality of electrodes disposed on a
substrate;a hinge electrically connected to at least one of the
electrodes and the hinge stands on said substrate extending along
substantially a vertical direction from said substrate; andsaid hinge
support a mirror disposed on top of said hinge along substantially a
horizontal direction wherein a width of said hinge is greater than or
equal to a length of said hinge and said length of said hinge is greater
than a thickness of said hinge.

3. The mirror device according to claim 1, wherein:a length of the hinge
is approximately 2 μm or smaller, andthe mirror is substantially a
square mirror wherein each side of said square mirror having a length
approximately 10 μm or smaller.

4. The mirror device according to claim 2, wherein:a length of the hinge
is approximately 2 μm or smaller, andthe mirror is substantially a
square mirror wherein each side of said square mirror having a length
approximately 10 μm or smaller.

5. A projection apparatus comprising a mirror device including a plurality
of mirror elements for reflecting an incident light projected from a
light thereto wherein:the mirror device further comprises a mirror
disposed on top of and supported on a vertical hinge extending
substantially along a vertical direction from a substrate; anda hinge
electrode disposed on the substrate and electrically connected to the
hinge, anda control circuit including a capacitor placed inside the
substrate, andan electrode disposed inside said substrate under a top
surface of said substrate and connected to the control circuit.

6. The projection apparatus according to claim 5, wherein:a length of the
hinge is approximately 2 μm or smaller, andthe mirror is substantially
a square mirror wherein each side of said square mirror having a length
approximately 10 μm or smaller.

7. The projection apparatus according to claim 5, wherein:the surface of
the electrode and the surface of the hinge electrode having approximately
a height from a top surface of said substrate.

8. The projection apparatus according to claim 5, wherein:the surface of
the electrode comprises a protective layer composed of silicon.

9. The projection apparatus according to claim 5, wherein:the light source
is a laser light source.

10. The projection apparatus according to claim 5, further comprising:a
barrier layer disposed between the hinge and mirror, and/or between the
hinge and the electrode.

11. The projection apparatus according to claim 5, comprising:at least two
electrodes disposed near said hinge and at least one of said two
electrode is disposed on the substrate.

12. The projection apparatus according to claim 5, wherein:a top surface
of the mirror comprising a surface structure with a step having a depth
and height relative to said top surface of the mirror wherein said depth
or height are substantially smaller than a wavelength of said incident
light projected from the light source.

13. The projection apparatus according to claim 5, wherein:at least a part
of the electrode is formed as a convex electrode relative to a top
surface of the substrate, andthe deflection angle of the mirror is
maintained constant by configuring an electrode as a stopper for
contacting said mirror thus prevent said mirror from further deflections.

14. The projection apparatus according to claim 5, wherein:said hinge
support a mirror disposed on top of said hinge along substantially a
horizontal direction wherein a cross sectional area of said hinge near
the electrode is less than or equal to a cross sectional area of said
hinge near said mirror.

15. The projection apparatus according to claim 5, wherein:said hinge
support a mirror disposed on top of said hinge along substantially a
horizontal direction wherein a width of said hinge is greater than or
equal to a length of said hinge and said length of said hinge is greater
than a thickness of said hinge.

Description:

CROSS REFERENCE TO RELATED APPLICATIONS

[0001]This application is a Divisional Application of a co-pending patent
application Ser. No. 11/894,248 filed on Aug. 18, 2007. The application
Ser. No. 11/894,248 is a non-provisional Application of a Provisional
Application 60/841,173 filed on Aug. 30, 2006 and a Continuation in Part
(CIP) Application of a pending U.S. patent application Ser. No.
11/121,543 filed on May 4, 2005. The application Ser. No. 11/121,543 is a
Continuation in part (CIP) Application of three previously filed
Applications. These three Applications are Ser. No. 10/698,620 filed on
Nov. 1, 2003, Ser. No. 10/699,140 filed on Nov. 1, 2003, and Ser. No.
10/699,143 filed on Nov. 1, 2003 by one of the Applicants of this Patent
Application. The disclosures made in these Patent Applications are hereby
incorporated by reference in this Patent Application.

BACKGROUND OF THE INVENTION

[0002]1. Field of the Invention

[0003]The present invention relates to a special light modulator for
modulating light and in particular to mirror device constituted by a
mirror element characterized by a hinge supporting the mirror and by an
electrode controlling the mirror. It also relates to a production method
for such a mirror device and to a projection apparatus comprising such a
mirror device.

[0004]2. Description of the Related Art

[0005]Even though there are significant advances of the technologies for
implementing an electromechanical mirror device as a spatial light
modulator (SLM) in recent years, there are still limitations and
difficulties when it is employed to provide a high quality image.
Specifically, when the images are digitally controlled, the image quality
is adversely affected due to the fact that the images are not displayed
with a sufficient number of gray scales.

[0006]An electromechanical mirror device is drawing a considerable
interest as a spatial light modulator (SLM). The electromechanical mirror
device consists of a "mirror array" arranging a large number of mirror
elements. In general, the mirror elements ranging from 60,000 to several
millions of pieces are arranged on a surface of a substrate in an
electromechanical mirror device.

[0007]Referring to FIG. 1A, an image display system 1 including a screen 2
is disclosed in a reference U.S. Pat. No. 5,214,420. A light source 10 is
used for generating light energy for illuminating the screen 2. The
generated light 9 is further concentrated and directed toward a lens 12
by a mirror 11. Lenses 12, 13 and 14 form a beam columnator operative to
columnate light 9 into a column of light 8. A spatial light modulator
(SLM) 15 is controlled on the basis of data input by a computer 19 via a
bus 18 and selectively redirects the portions of light from a path 7
toward an enlarger lens 5 and onto screen 2. The SLM 15 has a mirror
array arraying switchable reflective elements 17, 27, 37, and 47 being
consisted of a mirror 33 connected by a hinge 30 on a surface 16 of a
substrate in the electromechanical mirror device as shown in FIG. 1B.
When the element 17 is in one position, a portion of the light from the
path 7 is redirected along a path 6 to lens 5 where it is enlarged or
spread along the path 4 to impinge on the screen 2 so as to form an
illuminated pixel 3. When the element 17 is in another position, the
light is not redirected toward screen 2 and hence the pixel 3 is dark.

[0008]Each of mirror elements constituting a mirror device is to function
as spatial light modulator (SLM) and each mirror element comprises a
mirror and electrodes. A voltage applied to the electrode(s) generates a
coulomb force between the mirror and the electrode(s), thereby making it
possible to control and incline the mirror, and the mirror is "deflected"
according to a common term used in this specification for describing the
operational condition of a mirror element.

[0009]When a mirror is deflected by a voltage applied to the electrode(s)
for controlling the mirror, the deflected mirror also changes the
direction of the reflected light in reflecting the incident light. The
direction of the reflected light is changed in accordance with the
deflection angle of the mirror. The present specification refers to a
state of the mirror when the light of which almost the entirety of the
incident light is reflected to a projection path designated for image
display as an "ON light", while it refers to the light reflected to a
direction other than the designated projection path for image display as
an "OFF light".

[0010]And a state of the mirror that reflects the light of the incident
light in a manner that the ratio of the light, which is reflected to a
projection path (i.e., the ON light), to that which is reflected so as to
shift from the projection path (i.e., the OFF light) is referred to as a
specific ratio. And that the light reflected to the projection path with
a smaller quantity of light than the state of the ON light is referred to
as an "intermediate light".

[0011]The terminology of present specification defines an angle of
rotation along a clockwise (CW) direction as a positive (+) angle and
that of counterclockwise (CCW) direction as negative (-) angle. A
deflection angle is defined as zero degree (0°) when the mirror is
in the initial state, as a reference of mirror deflection angle.

[0012]Most of the conventional image display devices such as the devices
disclosed in a U.S. Pat. No. 5,214,420 implements a dual-state mirror
control that controls the mirrors in a state of either ON or OFF. The
quality of an image display is limited due to the limited number of gray
scales. Specifically, in a conventional control circuit that applies a
PWM (Pulse Width Modulation), the quality of the image is limited by the
LSB (least significant bit) or the least pulse width as a control related
to the ON or OFF state. Since the mirror is controlled to operate in
either the ON or OFF state, the conventional image projection apparatus
has no way to provide a pulse width for controlling the mirror that is
shorter than the control duration allowable on the basis of the LSB. The
least quantity of light, which is determined on the basis of the gray
scale, is the light reflected during the time duration based on the least
pulse width. The limited number of gray scales leads to a degradation of
the image.

[0013]Specifically, FIG. 1c exemplifies a control circuit for controlling
a mirror element according to the disclosure in the U.S. Pat. No.
5,285,407. The control circuit includes a memory cell 32. Various
transistors are referred to as "M*", where "*" designates a transistor
number and each transistor is an insulated gate field effect transistor.
Transistors M5 and M7 are p-channel transistors; while transistors M6,
M8, and M9 are n-channel transistors. The capacitances C1 and C2
represent the capacitive loads in the memory cell 32. The memory cell 32
includes an access switch transistor M9 and a latch 32a, which is based
on a Static Random Access switch Memory (SRAM) design. The transistor M9
connected to a Row-line receives a data signal via a Bit-line. The memory
cell 32 written data is accessed when the transistor M9 that has received
the ROW signal on a Word-line is turned on. The latch 32a consists of two
cross-coupled inverters, i.e., M5/M6 and M7/M8, which permit two stable
states, that is, a state 1 is Node A high and Node B low, and a state 2
is Node A low and Node B high.

[0014]The mirror is driven by a voltage applied to the address electrode
abutting an address electrode and is held at a predetermined deflection
angle on the address electrode. An elastic "landing chip" is formed at a
portion on the address electrode, which makes the address electrode
contact with mirror, and assists the operation for deflecting the mirror
toward the opposite direction when a deflection of the mirror is
switched. The landing chip is designed as having the same potential with
the address electrode, so that a shorting is prevented when the address
electrode is in contact with the mirror.

[0015]Each mirror formed on a device substrate has a square or rectangular
shape and each side has a length of 10 to 15 μm. However, in this
configuration, an unexpected reflected light for projecting image is
generated by reflection on the substrate of incident light through the
gap between adjacent mirrors. The contrast of an image display generated
by adjacent mirrors is degraded due to the reflections generated not by
the mirrors but by the gaps between the mirrors. As a result, a quality
of the image display is degraded. In order to overcome such problems, the
mirrors are arrayed on a semiconductor wafer substrate with a layout to
minimize the gaps between the mirrors. One mirror device is generally
designed to include an appropriate number of mirror elements wherein each
mirror element is manufactured as a deflectable mirror on the substrate
for displaying a pixel of an image. The appropriate number of elements
for displaying an image is in compliance with the display resolution
standard according to a VESA Standard defined by Video Electronics
Standards Association or television broadcast standards. In the case of
the mirror device comprising a plurality of mirror elements corresponding
to Wide eXtended Graphics Array (WXGA), whose resolution is 1280 by 768,
defined by VESA, the pitch between the mirrors of the mirror device is 10
μm and the diagonal length of the mirror array is about 0.6 inches.

[0016]The control circuit as illustrated in FIG. 1c controls the mirrors
to switch between two states and the control circuit drives the mirror to
oscillate in either the ON or OFF deflected angle (or position).

[0017]The minimum quantity of light controllable to reflect from each
mirror element for image display, i.e., the resolution of gray scale of
image display for a digitally controlled image projection apparatus, is
determined by the least length of time that the mirror is controllable to
hold at the ON position. The length of time that each mirror is
controlled to hold at an ON position is in turn controlled by multiple
bit words. FIG. 1D shows the "binary time periods" in the case of
controlling an SLM by four-bit words. As shown in FIG. 1D, the time
periods have relative values of 1, 2, 4, and 8 that in turn determine the
relative quantity of light of each of the four bits, where the "1" is
least significant bit (LSB) and the "8" is the most significant bit.
According to the Pulse Width Modulation (PWM) control mechanism, the
minimum quantity of light that determines the resolution of the gray
scale is a brightness controlled by using the "least significant bit" for
holding the mirror at an ON position during a shortest controllable
length of time.

[0018]In a simple example with n-bit word for controlling the gray scale,
one frame time is divided into (2n-1) equal time slices. If one
frame time is 16.7 msec., each time slice is 16.7/(2n-1) msec.

[0019]Having set these time lengths for each pixel in each frame of the
image, the quantity of light in a pixel which is quantified as "0" time
slices is black (i.e., no quantity of light), "1" time slice is the
quantity of light represented by the LSB, and 15 time slices (in the case
of n=4) is the quantity of light represented by the maximum brightness.
Based on the light being quantified, the time of mirror being held at the
ON position during one frame period is determined by each pixel. Thus,
each pixel with a quantified value which is more than "0" time slice is
displayed for the screen by the mirror being held at the ON position with
the number of time slices corresponding to its quantity of light during
one frame period. The viewer's eye integrates the brightness of each
pixel in such a manner that the image is displayed as if the image were
generated with analog levels of light.

[0020]For controlling deflectable mirror devices, the PWM calls for the
data to be formatted into "bit-planes", where each bit-plane corresponds
to a bit weight of the quantity of light. Thus, when the brightness of
each pixel is represented by an n-bit value, each frame of data has the
n-bit planes. Then, each bit-plane has a "0" or "1" value for each mirror
element. In the PWM described in the preceding paragraphs, each bit-plane
is independently loaded and the mirror elements are controlled on the
basis of bit-plane values corresponding to them during one frame. For
example, the bit-plane representing the LSB of each pixel is displayed as
a "1" time slice.

[0021]When adjacent image pixels are displayed with a very coarse gray
scales caused by great differences of quantity of light, thus, artifacts
are shown between these adjacent image pixels. That leads to the
degradations of image qualities. The degradations of image qualities are
specially pronounced in bright areas of image when there are "bigger
gaps" of gray scale, i.e. quantity of light, between adjacent image
pixels. The artifacts are caused by a technical limitation that the
digitally controlled image does not obtain a sufficient number of gray
scales, i.e. the levels of the quantity of light.

[0022]The mirrors are controlled either at the ON or OFF position. Then,
the quantity of light of a displayed image is determined by the length of
time each mirror is held, which is at the ON position. In order to
increase the number of levels of the quantity of light, the switching
speed of the ON or OFF positions for the mirror must be increased.
Therefore the digitally control signals need be increased to a higher
number of bits. However, when the switching speed of the mirror
deflection is increased, a stronger hinge for supporting the mirror is
necessary to sustain a required number of switches of the ON or OFF
positions for the mirror deflection. Furthermore, in order to drive the
mirrors provided with a strengthened hinge to the ON or OFF position,
applying a higher voltage to the electrode is required. The higher
voltage may exceed twenty volts and may even be as high as thirty volts.
The mirrors produced by applying the CMOS technologies probably is not
appropriate for operating the mirror at such a high range of voltages,
and therefore the DMOS mirror devices may be required. In order to
achieve a control of a higher number of gray scales, a more complicated
production process and larger device areas are required to produce the
DMOS mirror. Conventional mirror controls are therefore faced with a
technical problem that the good accuracy of gray scales and range of the
operable voltage have to be sacrificed for the benefits of a smaller
image projection apparatus.

[0023]There are many patents related to the control of quantity of light.
These Patents include the U.S. Pat. Nos. 5,589,852, 6,232,963, 6,592,227,
6,648,476, and 6,819,064. There are further patents and patent
applications related to different sorts of light sources. These Patents
include the U.S. Pat. Nos. 5,442,414, 6,036,318 and Application
20030147052. Also, The U.S. Pat. No. 6,746,123 has disclosed particular
polarized light sources for preventing the loss of light. However, these
patents or patent applications do not provide an effective solution to
attain a sufficient number of gray scales in the digitally controlled
image display system.

[0024]Furthermore, there are many patents related to a spatial light
modulation that includes the U.S. Pat. Nos. 2,025,143, 2,682,010,
2,681,423, 4,087,810, 4,292,732, 4,405,209, 4,454,541, 4,592,628,
4,767,192, 4,842,396, 4,907,862, 5,214,420, 5,287,096, 5,506,597, and
5,489,952. However, these inventions do not provide a direct solution for
a person skilled in the art to overcome the above-discussed limitations
and difficulties.

[0025]In view of the above problems, an invention has disclosed a method
for controlling the deflection angle of the mirror to express higher
number of gray scales of an image in a US Patent Application 20050190429.
In this disclosure, the quantity of light obtained during the oscillation
period of the mirror is about 25% to 37% of the quantity of light
obtained during the mirror is held on the ON position at all times.

[0026]According to such control, it is not particularly necessary to drive
the mirror at high speed. Also, it is possible to provide a higher number
of gray scales using a low elastic constant of the hinge that supports
the mirror. Hence, such control makes it possible to reduce the voltage
applied to the address electrode.

[0027]An image projection apparatus using the mirror device described
above is broadly categorized into two types, i.e., a single-plate image
projection apparatus implemented with only one spatial light modulator
and a multi-plate image projection apparatus implemented with a plurality
of spatial light modulators. In the single-plate image projection
apparatus, a color image is displayed by changing in turn the colors,
i.e. frequency or wavelength of projected light is changed by time. In a
multi-plate image projection apparatus, a color image is displayed by
allowing the spatial light modulators corresponding to beams of light
having different colors, i.e. frequencies or wavelengths of the light, to
modulate the beams of light; and combined with the modulated beams of
light at all times.

[0028]In these days, high resolutions such as a full high-definition (Full
HD: 1920 by 1080 pixels) are required on the filed of a projection
apparatus, prompting the design and development of a higher resolution
display.

[0029]A mirror device used in such a projection apparatus is constituted
by a mirror array arraying one to two million mirror elements in a
two-dimensional array.

[0030]The size of a mirror of the mirror element of a common mirror device
is a square of 11 μm. The wiring process rule of a CMOS circuit unit
of a memory cell for driving the mirror is configured to be 0.25 μm.
The mirror is controlled by setting the operating voltage of the memory
cell or mirror drive voltage, which is set to more than twenty volts.
Such a mirror is supported by an elastic hinge.

[0031]A common mirror device used for a Full High Definition (Full-HD) is
the diagonal size of 24.13 mm (0.95 inches), with the mirror pitch of 11
μm. An eXtended Graphics Array (XGA)-size mirror device has the
diagonal size of 17.78 mm (0.7 inches) of the mirror array, with the
mirror pitch of 14 μm.

[0032]FIG. 2 is a diagonal view of a mirror device arraying, in
two-dimension on a device substrate, mirror elements controlling a
reflection direction of incident light by deflecting the mirror.

[0033]The mirror device 200 shown in FIG. 2 is constituted by arraying a
plurality of mirror elements, each mirror element 300 is constituted by
address electrode (not shown in a drawing herein), elastic hinge (not
shown in a drawing herein) and a mirror supported by the elastic hinge,
lengthwise and crosswise (in two-dimension) on a device substrate 303.
FIG. 2 illustrates a case of arraying a plurality of mirror elements
respectively comprising square mirrors 302 lengthwise and crosswise at a
constant interval on the device substrate 303. The mirror 302 of one
mirror element 300 is controlled by applying a voltage to the address
electrode provided on the device substrate 303.

[0034]And a deflection axis 201 for deflecting the mirror 302 is indicated
by the dotted line. The light emitted from a light source 301 is incident
to the mirror 302 so as to be orthogonal or diagonal to the deflection
axis 201.

[0035]Note that the present specification document calls the distance
between the deflection axes of adjacent mirrors 302 as pitch and the
distance between the respective sides of the present mirror and adjacent
mirror 302 as gap.

[0036]The following is a description on an operation of one mirror element
300 by referring to the cross-sectional line II-II of the one mirror
element 300 of the mirror device 200 shown in FIG. 2.

[0037]FIGS. 3A and 3B are cross-sectional diagrams of one mirror element
in the line II-II of the mirror device shown in FIG. 2.

[0038]The one mirror element 300 comprises a mirror 302, an elastic hinge
304 supporting the mirror 302, address electrodes 307a and 307b, and two
memory cells including a first memory cell and a second memory cell both
for applying a voltage to the address electrodes 307a and 307b in order
to control the mirror 302 under a desired deflection state. The drive
circuits for the respective memory cells are provided in the inside of
the device substrate 303 so that a control of each memory cell based on
the signal of image data makes it possible to control the deflection
angle of the mirror 302, and modulate and reflect the incident light.

[0039]FIG. 3A is a cross-sectional diagram of a mirror element reflecting
incident light to a projection optical system by deflecting the mirror.

[0040]An application of a signal (0, 1) to a memory cell applies a voltage
of "0" volt to the address electrode 307a and that of Va volts to the
address electrode 307b, both shown in FIG. 3A. As a result, the mirror
302 is drawn by a coulomb force and deflected from the horizontal state
to the direction of the address electrode 307b to which a voltage of Va
volts is applied. This results in reflecting the incident light on the
mirror 302 to the projection optical system (which is called an ON light
state). Note that an insulation layer 306 is applied onto the device
electrode 303, and a hinge electrode 305 connected to the elastic hinge
304 is grounded through a Via (not shown in a drawing herein) disposed in
the insulation layer 306.

[0041]FIG. 3B is a cross-sectional diagram of a mirror element not
reflecting the incident light to the projection optical system by
deflecting the mirror.

[0042]An application of a signal (1, 0) to a memory cell applies a voltage
of Va volts to the address electrode 307a and that of "0" volt to the
address electrode 307b. As a result, the mirror 302 is drawn by a coulomb
force and deflected from the horizontal state to the direction of the
address electrode 307a to which a voltage of Va volts is applied. This
results in reflecting the incident light to the outside of the projection
optical system (which is called an OFF light state).

[0043]Incidentally, the coulomb force generated between the mirror 302 and
address electrode 307a, or 307b, is expressed by the following
expression:

F=k'e SV2/2h2 (1);

[0044]where S is the area size of the address electrode 307a or 307b, h is
the distance between the mirror 302 and address electrode 307a or 307b, e
is the permittivity between the mirror 302 and address electrode 307a or
307b, V is the voltage applied to the address electrode 307a or 307b, and
k' is a correction coefficient.

[0045]FIG. 4 is a cross-sectional diagram exemplifying a situation of
operating each mirror element disposed on the device substrate shown in
FIG. 2.

[0046]An independent operation of the each mirror element 300 in the ON
light state or OFF light state as shown in FIGS. 3A and 3B controls the
direction of reflection of the incident light. Here, the incident light
to the side edges of the mirror 302 is diffused to directions other than
the desired direction when the light is reflected. And the incident light
going through the gap between the adjacent mirrors 302 is reflected on
the device substrate 303, thus generating an extraneous reflection light.

[0047]Meanwhile, in the mirror 302 illuminated by the incident light, a
diffraction light is generated in a direction orthogonal to each side of
the mirror 302. If these components of diffusion light and extraneous
diffraction light enter the eye of the projection lens of the projection
apparatus, the contrast of an image is degraded.

[0048]A few characteristic mirrors 302 are disclosed as the mirrors 302 of
such mirror elements 300 of the above described mirror device 200.

[0049]One example is a U.S. Pat. No. 6,128,121 disclosing a mirror
comprising an opening part at the center of the support layer of the
mirror, on which a reflection member is layered.

[0050]Such a mirror 302, however, comprising the opening part at the
center of the support layer, allows a small step nearby the opening part
of the layered reflection member. This step allows a generation of an
extraneous diffraction light from the center of the mirror 302. And the
diffraction light entering the projection lens 309 causes the problem of
degrading the contrast of an image.

[0051]FIG. 5 illustrates a mirror comprising an opening part at the center
of the support layer of the mirror 302, on which a reflection member is
layered. Note that this delineates by emphasizing a step 552 of the
reflection member at the center.

[0052]An illumination, on the step 552 nearby the opening part of the
mirror 302, of the light 551 emitted from the light source 301 generates
diffraction light 553 in a direction orthogonal to a side orthogonal to a
direction of light illuminated on the step 552 of the opening. And the
incidence of the diffraction light 553 to the projection lens degrades
the contrast of an image. Therefore, the mirror must be designed by
considering such an influence of the diffraction light 553.

[0053]The mirror device as described above can normally be produced
through a process similar to the production process for a semiconductor.
The production process primarily includes chemical vapor deposition
(CVD), photolithography, etching, doping, chemical mechanical polishing
(CMP), et cetera.

[0054]Next, in order to respond to a high resolution projection apparatus,
the number of mirror elements must also be increased, requiring a
miniaturization of a mirror size of the mirror element. An increase of
the number of mirror elements without miniaturizing the mirror size
enlarges the size of the mirror array proportionately with the number of
mirror elements. And brought about is a problem of an enlarged mirror
device enlarging the entirety of the optical system of the projection
apparatus, resulting in enlarging the projection apparatus per se.
Therefore, an important challenge for solving the problem of enlarged
projection apparatus associated with the high resolution projection
apparatus is a response to the miniaturization of the mirror size of a
mirror element.

[0055]Also required for miniaturizing the mirror size is a miniaturization
of the memory cell and structure body disposed under the mirror. For
miniaturizing the memory cell, the wiring process rule for a MOS circuit
of the memory cell also needs to be miniaturized. Once the wiring process
rule is miniaturized, the operating voltage of an FET transistor or such
is decreased, and a voltage applicable to an individual address electrode
for controlling the deflection of a mirror is decreased. If the
deflection of a mirror is controlled in such a configuration without
improving an elastic hinge, a voltage to be applied to the address
electrode needs to be increased in order to control the deflection of the
mirror. Consequently ushered in is a problem such as a circuit formed in
the device substrate (e.g., the withstand voltage of a transistor, the
capacitance of a DRAM capacitor, et cetera) needing to be increased for
increasing the voltage to be applied to the address electrode. In order
to solve such a problem, the elastic hinge also needs to be miniaturized.
The elastic hinge, however, is very thin and small as compared to the
mirror, requiring a consideration for the endurance against a repetition
of usages as well as considerations for the method of supporting the
mirror and for the endurance against usage environments and temperature
changes in order to achieve a miniaturization of the elastic hinge, thus
a difficulty accompanies the miniaturization of the elastic hinge.

[0056]Meanwhile, an enforcement of a restitution force of the elastic
hinge makes it possible to speed up the deflecting operation of the
mirror. A speedier deflection control enables a minute adjustment of a
light intensity and an obtainment of a higher level-gray scale of an
image. A reinforcement of the elastic hinge for an improved restitution
force thereof (e.g., increasing the thickness of the elastic hinge),
however, requires an increased voltage to be applied to the address
electrode, requiring a larger area size thereof. In terms of this point,
the elastic hinge is conventionally placed at the center of a mirror,
thus limiting the design of a mirror element, such as the form and area
size of the address electrode, and therefore a hurdle exists in enlarging
the area size of the address electrode as well.

[0057]The following lists reference patent documents related to the
structures of conventional mirror devices and the technique for producing
such mirror devices.

[0058]U.S. Pat. No. 5,214,420: this document has disclosed a structure of
a mirror device.

[0059]U.S. Pat. No. 5,936,760: this document has disclosed a mirror device
implemented with a hinge by putting a hole in the sacrifice layer.

[0068]A purpose of the present invention is to configure a mirror device
comprising a mirror element overcoming the above noted problem. Another
purpose is to produce such a mirror device. Yet another purpose is to
provide a projection apparatus comprising such a mirror device.

[0069]A first aspect of the present invention is to provide a mirror
device, comprising: a plurality of electrodes equipped on a substrate; a
hinge connected to at least one of the electrodes; a mirror connected to
the hinge and corresponding to at least one of the electrodes, wherein a
barrier layer is comprised between the hinge and mirror, and/or between
the hinge and electrode.

[0070]A second aspect of the present invention is to provide a projection
apparatus, comprising: a mirror device comprising a plurality of mirror
elements reflecting the light emitted from a light source; and a
projection optical system for projecting the light reflected by the
mirror device, wherein the mirror device comprises a mirror for
reflecting the light, a hinge for supporting the mirror, a substrate for
supporting the hinge, a hinge electrode equipped within the substrate and
electrically conductive to the hinge, a control circuit including a
capacitor placed in the inside of the substrate, and an electrode
connected to the control circuit.

[0071]A third aspect of the present invention is to provide a mirror
device production method, comprising the steps of: forming a circuit and
a wiring on a substrate; forming an electrode connected to both the
wiring and the circuit on the substrate, forming a sacrifice layer on the
surfaces of the substrate and electrode, putting a hole from the surface
of the sacrifice layer to the electrode, forming a hinge layer in the
hole which has been put and on the sacrifice layer, etching the hinge
layer by using a mask, forming a barrier layer on the etched hinge layer,
forming a mirror layer on the hinge layer and barrier layer, and forming
a protective layer on the mirror layer by employing a chemical vapor
deposition (CVD).

BRIEF DESCRIPTION OF THE DRAWINGS

[0072]FIG. 1A shows a prior art illustrating the basic principle of a
projection display using a micromirror device;

[0073]FIG. 1B shows a prior art illustrating the basic principle of a
micromirror device used for a projection display;

[0076]FIG. 2 is a diagonal view of a mirror device arraying, in
two-dimension on a device substrate, mirror elements controlling a
reflection direction of incident light by deflecting the mirror;

[0077]FIG. 3A is a cross-sectional diagram of a mirror element reflecting
incident light to a projection optical system by deflecting the mirror;

[0078]FIG. 3B is a cross-sectional diagram of a mirror element not
reflecting the incident light to the projection optical system by
deflecting the mirror;

[0079]FIG. 4 is a cross-sectional diagram exemplifying a situation of
operating each mirror element equipped on the device substrate shown in
FIG. 2;

[0080]FIG. 5 illustrates a mirror comprising an opening part at the center
of the support layer of the mirror, with a reflection member being
layered on the opening part;

[0081]FIG. 6 is a plain view diagram, and a cross-sectional diagram, of a
mirror element of a mirror device according to a preferred embodiment 1;

[0082]FIG. 7A is a plain view, and a cross-sectional diagram, of a mirror
element of a mirror device according to a preferred embodiment 2;

[0083]FIG. 7B exemplifies a support layer of a mirror of a mirror element
shown on the top left side of FIG. 7A;

[0084]FIG. 8 is a plain view diagram, and a cross-sectional diagram, of a
modified example of the mirror element shown in FIG. 7A;

[0085]FIG. 9A is a cross-sectional diagram of a mirror element of a mirror
device according to a preferred embodiment 3;

[0086]FIG. 9B is a plain view diagram of a surface of a semiconductor
wafer substrate of a mirror device according to the embodiment 3;

[0087]FIG. 9C is a plain view diagram of a mirror element of a mirror
device of the embodiment 3 with a mirror being removed;

[0088]FIG. 9D is a cross-sectional diagram when a mirror of the mirror
element shown in FIG. 9A is deflected to an ON state;

[0089]FIG. 9E is a cross-sectional diagram when a mirror of the mirror
element shown in FIG. 9A is deflected to an OFF state;

[0090]FIG. 10A is a cross-sectional diagram of one mirror element of a
mirror device for describing a production process of the mirror device;

[0091]FIG. 10B is a cross-sectional diagram of one mirror element of a
mirror device for describing a production process of the mirror device;

[0092]FIG. 11A is a plain view diagram of a mirror element viewing from
the arrow direction III in the step 3 of FIG. 10A;

[0093]FIG. 11B is a plain view diagram of a mirror element viewing from
the arrow direction IV in the step 6 of FIG. 10A;

[0094]FIG. 12A is a cross-sectional diagram of one mirror element of a
mirror device comprising two million mirror elements for describing a
production process of the mirror device;

[0095]FIG. 12B is a cross-sectional diagram of one mirror element of a
mirror device comprising two million mirror elements for describing a
production process of the mirror device;

[0096]FIG. 12C is a cross-sectional diagram of one mirror element of a
mirror device comprising two million mirror elements for describing a
production process of the mirror device;

[0097]FIG. 13A is a plain view diagram of a mirror element viewing from
the arrow direction XXVI in the step 26 of FIG. 12B;

[0098]FIG. 13B is a diagram showing an elastic hinge and a mirror
constructed on a center electrode of a mirror element of a mirror device
formed in the production processes shown in FIGS. 12A through 12C;

[0099]FIG. 14 is a configuration diagram of a single-plate projection
apparatus comprising a mirror device according to the present embodiment;

[0100]FIG. 15A is a front view diagram of a configuration of a two-plate
projection apparatus comprising two mirror devices including the mirror
device according to the present embodiment;

[0101]FIG. 15B is a rear view diagram of a configuration of the two-plate
projection apparatus shown in FIG. 15A;

[0102]FIG. 15C is a side view diagram of a configuration of the two-plate
projection apparatus shown in FIG. 15A;

[0103]FIG. 15D is a plain view diagram of a configuration of the two-plate
projection apparatus shown in FIG. 15A; and

[0104]FIG. 16 is a configuration diagram of a three-plate projection
apparatus comprising three mirror devices including the mirror device
according to the present embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0105]Reference is now made to the above listed Figures for the purpose of
describing, in detail, the preferred embodiments of the present
invention. The Figures referred to and the accompanying descriptions are
provided only as examples of the invention and are not intended in anyway
to limit the scope of the claims appended to the detailed description of
the embodiment.

[0106]In an exemplary embodiment, this invention discloses a mirror
device, comprising: a plurality of electrodes equipped on a substrate; a
hinge connected to at least one of the electrodes; a mirror connected to
the hinge and corresponding to at least one of the electrodes, wherein a
barrier layer is comprised between the hinge and mirror, and/or between
the hinge and electrode. Also noted is a mirror device production method
for producing such-configured mirror device. Further noted is a
projection apparatus comprising such-configured mirror device.

[0107]The following is a description of the structure and operation of a
mirror element of a mirror device according to the present embodiment,
the production method of the mirror device according to the present
embodiment and a projection apparatus comprising the mirror device
according to the present embodiment.

Embodiment 1

[0108]FIG. 6 is plain view and cross-sectional diagrams of a mirror
element of a mirror device according to a preferred embodiment 1.

[0109]The top left drawing of FIG. 6 is the plain view of four mirror
elements 650 of a mirror device according to the embodiment 1.

[0110]The first is a description on the configuration of each mirror
element 650 shown in FIG. 6.

[0111]A mirror 651 of each mirror element 650 shown in FIG. 6 is formed as
an approximate square such as square and parallelogram as an example. The
length of each of four sides of the mirror 651 is preferably between
approximately 4 to 10 μm. An application of a voltage to address
electrodes 653a and 653b generates a coulomb force to draw the mirror 651
and deflects it on the basis of a deflection axis. This results in
enabling a change of directions of reflecting the light illuminated on
the mirror 651. Note that FIG. 6 indicates the mirror 651 of each mirror
element by the dotted lines. And there is a layer called a support layer
656 under the mirror 651 and the layer is connected to an elastic hinge
652. The support layer 656 may alternatively be placed only in the
connection part with the elastic hinge 652 in place of the entire surface
under the mirror 651. Also, a connection member made from titanium (Ti),
tungsten (W), tantalum (Ta) or such may alternatively be equipped between
the elastic hinge 652 and support layer 656. The material of the mirror
is preferably made of aluminum (Al) that is a reflection member.

[0112]The elastic hinge 652 is shared between an edge part of a mirror 651
and that of a mirror adjacent to the present mirror 651, and connected to
the support layers 656 of both mirrors 651. The elastic hinge 652 shared
in the configuration of FIG. 6 is equipped in proximity to the deflection
axes of the respective mirrors 651 having the deflection axes in the same
direction. The elastic hinge 652 is featured with a groove in a gap part
between the individual mirrors 651. Such a configuration absorbs an
extraneous force as a result of the grooved part of the elastic hinge 652
deforming when one mirror 651 of the two sharing the elastic hinge 652 is
deflected, thereby practically eliminating an influence of the deflection
to the other mirror 651 sharing the elastic hinge 652. Therefore, it is
possible to control the individual mirrors 651 independently even if they
share the elastic hinge 652. The elastic hinge 652 is preferably to be
placed in a manner to maximize and equalize the area sizes of the address
electrodes 653a and 653b on the left and right sides of the deflection
axis of the mirror 651.

[0113]The material of the elastic hinge 652 is preferably an elastomer
including silicon (Si), such as amorphous silicon (a-Si) and single
crystal silicon, and may further be configured as a conductive hinge by
doping with arsenic or phosphorus. A same material as the support layer
656 is preferred.

[0114]Furthermore, the elastic hinge 652 is equipped on a hinge electrode
655 shared by the end part of the mirror 651 and the end part of a mirror
adjacent to the present mirror 651, as a hinge structural body for
supporting the elastic hinge 652. The hinge electrode 655 is grounded.
Note that the hinge structural body for supporting the elastic hinge 652
may alternatively be equipped separately from the hinge electrode 655.

[0115]The address electrodes 653a and 653b are placed under the mirror
651. An application of a voltage to the address electrodes 653a and 653b
generates a coulomb force between the mirror 651 and address electrode
653a, or 653b, thereby making it possible to deflect the mirror 651 in a
desired direction. Conventionally, an elastic hinge 652 is formed nearby
the center part of a mirror 651, requiring a placement of the address
electrodes 653a and 653b so as to avoid the elastic hinge 652, and
therefore the form and placement of the address electrodes 653a and 653b
have been limited. Whereas the present embodiment 1 is configured to
connect the elastic hinge 652 so as to share the end part of the mirror
651 and that of the adjacent mirror 651, thereby making it possible to
use the vicinity of the center part under the mirror 651. This allows a
placement of the address electrodes 653a and 653b in a free form nearby
the center part, increasing the freedom of the design of the mirror
element 650. This makes it possible to increase the area size of the
address electrodes 653a and 653b by using the vicinity of the center part
under the mirror 651 and therefore increase the coulomb force necessary
for deflecting the mirror 651. This results in decreasing the voltage to
be applied to the address electrodes 653a and 653b for deflecting the
mirror 651. In the case of being enabled to control the mirror 651 with a
low voltage while keeping the coulomb force at the same level, a DRAM
circuit as control circuit for the mirror 651 can be made more compact.
Therefore, the mirror element 650 can be made more compact. Moreover, it
is possible to control the mirror 651 by a low volt, thus reducing the
power consumption for controlling the mirror device.

[0116]Incidentally, the configuration shown in FIG. 6 is such that the
address electrodes 653a and 653b placed on the left and right sides under
the mirror 651 are formed practically as a triangle, with the area size
thereof being the same. Here, the form of the mirror 651, the form of the
elastic hinge 652, the form and height of the address electrodes 653a and
653b, and such, may be appropriately modified, and they may not
necessarily be configured to be symmetrical about the deflection axis of
the mirror.

[0117]The top right drawing of FIG. 6 is a diagram of a side view of the
cross-section of the line A-A' indicated in the plain view diagram of the
mirror element shown in the top left drawing of FIG. 6.

[0118]The mirror 651 is supported by the support layer 656, which is
connected to the elastic hinge 652 that is shared with the adjacent
mirror 651. That is, the elastic hinge 652 is connected to the end part
of the support layer 656 of the mirror 651 and to the end part of the
support layer 656 of a mirror adjacent to the present mirror 651. And the
elastic hinge 652 comprises a groove in line with the gap between the
adjacent mirrors 651. The elastic hinge 652 is connected to the hinge
electrode 655, which is shared between the mirror 651 and the adjacent
mirror 651 within a substrate 654. And the address electrodes 653a and
653b are placed on the substrate 654 under the mirror 651. The address
electrodes 653a and 653b are configured and applied with a voltage Va by
a control circuit (not shown in a drawing herein).

[0119]The bottom left drawing of FIG. 6 is a side view diagram of the
cross-section of the line B-B' of the plain view diagram of the mirror
element shown on the top left side of FIG. 6.

[0120]An application of a voltage Va to the address electrode 653a makes
the mirror 651 of the mirror element 650 deflect to the left side drawn
by a coulomb force generated between the address electrode 653a and
mirror 651. And the mirror 651 contacts with the address electrode 653a,
on the left, which is layered with an insulation film, thereby the
deflection of the mirror 651 being held at a constant angle. An
illumination of the incident light in the state of holding the deflection
angle of the mirror makes the illumination light reflected to a constant
direction.

[0121]As such, each of the mirror elements of the mirror device according
to the embodiment 1 is configured. Here, it is preferable to configure
the elastic hinge 652 of each mirror element 650 to have a length of 2
μm or smaller and the mirror 651 to be an approximate square of one
side being 10 μm or smaller. Note that the configuration is in a
manner to form the individual address electrodes 653a and 653b protruded
from the surface of the substrate 654 so that the mirror 651 contacts
with the corner of the individual address electrode 653a or 653b to make
it play the role of the stopper for the mirror 651, thereby holding the
deflection angle of the mirror 651 constant.

[0122]The present embodiment is configured to equip the elastic hinge 652
on the end part of the mirror 651, thereby making it possible to spread
the address electrodes 653a and 653b in the center area under the mirror
651 and enlarge the area size of the address electrodes 653a and 653b.
Such a configuration makes it possible to increase a coulomb force
working between the mirror 651 and address electrode 653a or 653b. A
larger coulomb force enables reinforcement (e.g., a larger thickness of
the elastic hinge) of the structure of the elastic hinge 652 so as to
support the mirror 651 more stably. Furthermore, a larger coulomb force
enables a quicker control of deflecting the mirror 651 and an improvement
of the gradation of an image as compared to the conventional technique.

Embodiment 2

[0123]FIG. 7A is a plain view diagram, and a cross-sectional diagram, of a
mirror element of a mirror device according to a preferred embodiment 2.

[0124]The top left drawing of FIG. 7A is a top plain view of four mirror
elements of a mirror device according to the embodiment 2.

[0125]Provided here is a description on a configuration of each mirror
element 700. Also in each mirror element 700 shown in FIG. 7A, a mirror
701 is deflected on the basis of the deflection axis by a coulomb force
generated by an application of a voltage to address electrode 703a or
703b. As a result, the reflecting direction of the light illuminated on
the mirror 701 can be changed. FIG. 7A also shows the mirror 701 of each
mirror element 700 delineated by the dotted lines. Provided in a part or
the entirety under each of the mirrors 701 is a layer called as support
layer 706 which is connected to two elastic hinges 702a and 702b equipped
on both end parts of one mirror. The support layer 706 may alternatively
be formed only on the joining parts with the elastic hinges 702a and
702b. The support layer 706 may alternatively be formed integrally with
the elastic hinges 702a and 702b. Furthermore, a joinder member made from
titanium (Ti), tungsten (W), tantrum (Ta) or such may be equipped between
the support layer 706 and elastic hinges 702a and 702b. The material for
the mirror 701 is preferably to use aluminum (Al) with high reflectance.

[0126]These elastic hinges 702a and 702b are equipped nearby the
deflection axis of the mirror 701. The configuration of FIG. 7A places
the elastic hinge 702a, which is equipped on the upper end part of the
mirror 701, on the right side of the deflection axis of the mirror 701,
while places the elastic hinge 702b, which is equipped on the lower end
part of the 701, on the left side of the deflection axis for equalizing
the area size of the address electrodes 703a and 703b positioned on the
left and right sides of the mirror 701. These elastic hinges 702a and
702b are preferably to be placed so as to maximize and equalize the area
sizes of the address electrodes 703a and 703b on the left and right sides
of the mirror 701. If one mirror is equipped with two elastic hinges as
described above, the thickness of the elastic hinge may be reduced to
half as compared to the conventional case of supporting a mirror with one
elastic hinge.

[0127]The equipment of the elastic hinges 702a and 702b separately in two
places under the end parts of the mirror 701 as described above makes it
possible to support the mirror 701 stably against a rotation of the
mirror surface in the horizontal direction. And the connection of the two
elastic hinges 702a and 702b to the same support layer 706 supports the
mirror 701 stably, withstanding an external vibration and leading to an
improvement of the durability of the mirror device.

[0128]And hinge electrodes 705 respectively corresponding to the two
elastic hinges 702a and 702b, which are equipped at both of the end parts
of the mirror 701, are equipped as hinge structural bodies for supporting
the respective elastic hinges 702a and 702b. The individual hinge
electrodes 705 are grounded. Note that the hinge structural bodies may
alternatively be equipped separately from the hinge electrodes 705.

[0129]The address electrodes 703a and 703b are placed under the mirror
701. An application of a voltage to the address electrode 703a or 703b
generates a coulomb force working between the mirror 701 and address
electrode 703a or 703b, making it possible to deflect the mirror 701. The
elastic hinge has conventionally been formed nearby the center part of a
mirror, limiting the form, placement and such, of address electrodes
positioned under the mirror. Whereas the present embodiment 2 is also
configured to equip the elastic hinges 702a and 702b at both of the end
parts of one mirror 701, thereby allowing a free usage of the vicinity of
the center part under the mirror 701. This accordingly makes it possible
to place the address electrodes 703a and 703b and such, freely in the
vicinity of the center part under the mirror 701. Also enabled is an
increase of the area size of the address electrodes 703a and 703b by
using the vicinity of the center part under the mirror 701 and,
therefore, an increase of the coulomb force for deflecting the mirror
701. As a result, a voltage to be applied to the address electrodes 703a
and 703b for deflecting the mirror 701 can be decreased. And the
capability of decreasing the voltage to be applied to the address
electrodes 703a and 703b makes it possible to make the mirror 701 more
compact, as described for the embodiment 1.

[0130]Note that the configuration of FIG. 7A has the form of the address
electrodes 703a and 703b positioned on the left and right sides of the
deflection axis of the mirror 701 thereunder featured as one edge of the
approximate triangle being cut off substantially, and equalizes the area
size of the address electrodes 703a and 703b by placing them
symmetrically about a point of the center of the mirror 701.

[0131]Stoppers 707 are placed and shared by the apexes of the mutually
adjacent individual mirrors 701. When the mirror 701 is deflected by a
coulomb force as a result of a voltage being applied to the address
electrodes 703a and 703b, the mirror 701 contacts with a stopper 707
makes the deflection angle of the mirror 701 constant, thus determining
the reflection of the light at a prescribed direction. An appropriate
adjustment of the height or such of the stopper 707 makes it possible to
determine the deflection angle of the mirror 701. A sharing of the
stopper 707 with the respective mirrors 701 makes it possible to not only
reduce the number thereof as compared to a conventional configuration but
also control so as to reflect the illumination light at practically the
same deflection angle as that of the adjacent mirrors 701. Note that the
form, thickness, height and such of the individual constituent component
of each of the mirror 701, support layer 706, elastic hinges 702a and
702b, stopper 707 and address electrodes 703a and 703b may be
appropriately modified.

[0132]And the individual structure, in place of integrating a stopper with
the address electrodes 703a and 703b, enables a prevention of stiction,
which can otherwise occur at the time of the mirror contacts with the
address electrode 703a or 703b.

[0133]The top left drawing of FIG. 7A is a view, from the right side, of
the cross-section on the line C-C' indicated in the plain view diagram of
the mirror element shown on the top left side of FIG. 7A. The mirror 701
is supported by the support layer 706, on both ends part of which is
connected to the two elastic hinges 702a and 702b. The elastic hinges
702a and 702b are connected to the respective hinge electrodes 705
corresponding to the individual elastic hinges 702a and 702b within the
substrate 704. The address electrodes 703a and 703b are placed on the
substrate 704 positioned under the mirror 701, and the address electrode
703a on the left side of the mirror 701 is placed in symmetry about a
point of the center of the mirror 701 and against the address electrode
703b on the right side of the mirror 701. And the individual address
electrodes 703a and 703b are provided with means for applying the voltage
Va from a control circuit (not shown in a drawing herein). The control
circuit is preferably to comprise dynamic random access memory (DRAM).

[0134]The bottom left drawing of FIG. 7A is a side view of the
cross-section on the line D-D' indicated in the plain view diagram of the
mirror element shown on the top left side of FIG. 7A.

[0135]When a voltage is applied to the address electrode 703a on the left
side, the mirror 701 of the mirror element 700 is deflected to the left
side by a coulomb force working between the address electrode 703a on the
left side and mirror 701. Then, the mirror 701 contacts with the stopper
707 shared with the adjacent mirror 701 maintain the deflection angle
constant. An illumination of the incident light in the state of
determining the deflection of the mirror 701 reflects the illumination
light in a prescribed direction. Such is a configuration of the
individual mirror elements 700 of the mirror device according to the
present embodiment 2.

[0136]The next is a description of an example of a support layer 706 of
the mirror element 700 shown on the top left of FIG. 7A by referring to
FIG. 7B.

[0137]FIG. 7B exemplifies a support layer 706 of the mirror 701 of a
mirror element 700 shown on the top left side of FIG. 7A.

[0138]The mirror 701 of FIG. 7A is placed on the support layer 706 shown
in FIG. 7B. The support layer 706 comprises cutout parts at the
respective connection parts with the elastic hinges 702a and 702b. In the
production process of the mirror, a sacrifice layer is layered uniformly
so as to cover on each support layer 906 and support layer be exposed by
polishing the deposited sacrifice layer, followed by layering the mirror
701. Since the thickness of the mirror 701 is merely a level of 1000 to
3000 angstroms, however, a slight step in response to the forms of the
surface for layering the mirror 701 is generated. This results in leaving
a slight step on the surface of the mirror 701 layered on the support
layer 706 in the cutout part. Meanwhile, FIG. 7B illustrates the
diffraction light generated at the time of illuminating the mirror 701
with the incident light from the direction orthogonal to the deflection
axis of the mirror 701.

[0139]The diffraction light 712 is generated in the direction orthogonal
to each side of the mirror 701 illuminated with the light, and therefore
the diffraction light 712 is generated in the direction of the left and
right arrows shown in FIG. 7B from the cutout part of both of the edges
of the mirror 701, to which the illumination light is incident, on the
mirror placed on the support layer 706 of FIG. 7B. In this case, the
diffraction light 912 is generated only at both of the sides, at the
cutout part, of the mirror 701 and therefore it is possible to lessen the
influence of the diffraction light entering the projection lens as
compared to the mirror shown for the conventional technique which has a
step in the center part of the mirror, generating the diffraction light
at the center part. Incidentally, it is preferable to configure the top
surface of the mirror 701 so as not to have a step of the depth or height
of the wavelength of the light emitted from the light source in order to
avoid an occurrence of a diffraction light 712 as much as possible.

[0140]The next exemplifies a modified embodiment of the mirror device of
the embodiment 2 by referring to FIG. 8. FIG. 8 is the plain view and
cross-sectional diagrams of a modified example of the mirror element 800
shown in FIG. 7A.

[0141]The top left drawing of FIG. 8 is the top plain view diagram of a
modified example of the four mirror elements shown in FIG. 7A. The mirror
element 800 of FIG. 8 comprises a center division line of the mirror 801
as the deflection axis thereof, which is different from the mirror
element 700 of FIG. 7A. It also equips elastic hinges 802a and 802b at
positions of the respective both end parts of the mirror 801 nearby the
deflection axis. The forms of address electrodes 703a and 703b, which are
shown in FIG. 7A, are changed so as to even out the area sizes of address
electrodes 803a and 803b on the left and right sides of the deflection
axis of the mirror 801.

[0142]Then, stoppers 807 are placed nearby the deflection axis, and the
sides, of each mirror 801 so as to share a stopper 807 between the
respective adjacent mirrors 801. And the mirror 801 contacts with the
corner of the stopper 807 at the time of the mirror 801 being deflected
by a coulomb force makes the deflection angle of the mirror 801 constant,
thereby determining the reflection of the illumination light in one
direction. An appropriate adjustment of the height or such of the stopper
807 makes it possible to determine the deflection angle of the mirror
807. The sharing of the stopper 807 between the respective adjacent
mirrors 801 makes it possible not only to reduce the number of stoppers
807 than that of the conventional technique, but also to enable the
reflection of the illumination light at approximately the same as the
mutually adjacent mirror 801.

[0143]As for the configuration other than the above description, the
elastic hinges 802a and 802b, address electrodes 803a and 803b and
stoppers 807 are placed symmetrically about a point of the center of the
mirror 801 likewise the configuration of FIG. 7A. Note that the elastic
hinges 802a and 802b are preferably to be placed so as to maximize and
equalize the area sizes of the address electrodes 803a and 803b on the
left and right sides of the deflection axis of the mirror 801. The
equipment of the elastic hinges 802a and 802b at the end parts of the
mirror thusly makes it possible to place the address electrodes 803a and
803b, and such, nearby the center part on the mirror 801 and increase the
area size of the address electrodes 803a and 803b nearby the center part.
This configuration results in increasing the coulomb force for deflecting
the mirror 801.

[0144]The top right drawing of FIG. 8 is a side view of the cross-section
of the line E-E' of the plain view diagram of the mirror element 800
shown on the top left side of FIG. 8. The mirror 801 is supported by a
support layer 806, the both end parts of which are connected to the two
elastic hinges 802a and 802b. The individual elastic hinges 802a and 802b
are connected to the respective hinge electrodes 805 corresponding to the
respective elastic hinges 802a and 802b within a substrate 804. The
individual address electrodes 803a and 803b are placed on the substrate
804 positioned under the mirror 801, with the address electrode 803a on
the left side of the mirror 801 being placed symmetrically about a point
of the center of the mirror 801 with respect to the address electrode
803b on the right side of the mirror 801. And the individual address
electrodes 803a and 803b are provided with means for applying a voltage
Va from a control circuit (not shown in a drawing herein). The control
circuit, comprising a capacitor, is connected to the address electrodes
803a and 803b, respectively. And the control circuit preferably comprises
dynamic random access memory (DRAM). Also configured is that the stopper
807 is placed nearby the elastic hinges 802a and 802b so as to make the
mirror 801 contacts with on a corner of the stopper 807 when the mirror
801 is deflected. The bottom left drawing of FIG. 8 is a side view of the
cross-section of the line F-F' of the plain view diagram of the mirror
element 800 shown on the top left of FIG. 8.

[0145]When a voltage is applied to the address electrode 803a on the left
side (with a voltage not being applied to the other address electrode
803b), the mirror 801 of the mirror element 800 is deflected to the left
side by a coulomb force working between the address electrode 803b on the
left and mirror 801. And the mirror 801 contacts with on the corner of
the stopper 807 which is shared with the adjacent mirror 801 maintains
the deflection angle of the mirror 801 constant. An illumination of the
incident light in the state of maintaining the deflection angle of the
mirror 801 reflects the illumination light in a prescribed direction
reflected by the mirror 801.

[0146]Such is the configuration of the individual mirror elements 800 of
FIG. 8. Note that it is preferable to configure the elastic hinge of each
mirror element 800 to have the length of 2 μm or smaller and the
mirror 801 of each mirror element to be an approximate square with the
side of 10 μm or smaller.

Embodiment 3

[0147]FIG. 9A is a cross-sectional diagram of a mirror element of a mirror
device according to a preferred embodiment 3.

[0148]The mirror element shown in FIG. 9A comprises a semiconductor wafer
substrate on which formed are the wirings 906a, 906b and 906c of a drive
circuit for driving and controlling a mirror 913, the first Vias 907a,
907b, 907c, 907d and 907e which are connected to the wiring 906a, 906b
and 906c of the drive circuit, a first insulation layer 901 and a second
insulation layer 902. Here, the wiring 906a on the left is equipped with
two first Vias 907c and 907e across the insulation layer 902, and the
wiring 906b on the right is likewise equipped with two first Vias 907b
and 907e across the insulation layer 902. The wiring 906c in the center
is equipped with only one Via 907a. As such, the present embodiment is
configured to equip three of wirings 906a, 906b and 906c and five of the
first Vias 907a, 907b, 907c, 907d and 907e in the insulation layer 902.

[0149]Note that the present embodiment is configured to equip the left and
right wirings respectively with two of the first Vias, the numbers of the
first Vias, however, may be different between the left and right wirings.
Also, the number of the first Vias may be larger or smaller than that
specified for the present embodiment. And second Vias 915a, 915b and 915c
and surface electrodes 908a and 908b are formed on the first Vias 907a,
907b, 907c, 907d and 907e, respectively, on the left and right.

[0150]The second Vias 915a, 915b and 915c are formed on the first Via
907a, which is formed on the wiring 906c at the center, and the first
Vias 907b and 907c, which are formed on the wirings 906a and 906b on the
left and right. Surface electrodes 908a and 908b are formed respectively
on the remaining first Vias 907d and 907e, on which second Via 915a, 915b
or 915c was not formed on the wirings 906a and 906b.

[0151]Then, a first protective layer 903 is accumulated on the insulation
layer 902 and a second protective layer 904 is formed on the first
protective layer 903.

[0154]The Vias 907a, 907b, 907c, 907d and 907e, and second Vias 915a, 915b
and 915c, are preferably constituted by a metal including tungsten or
cupper.

[0155]The surface electrodes 908a and 908b may use a material (e.g.,
tungsten or aluminum) be similar to that of the first Vias 907a, 907b,
907c, 907d and 907e and second Vias 915a, 915b and 915c, or a material
with high electrical conductivity such as aluminum. The form of the
surface electrodes 908a and 908b may be arbitrary. While the
configuration of FIG. 9A forms the surface electrodes 908a and 908b on
the first Vias 907d and 907e, they may be formed directly on the wirings
906a and 906b.

[0156]The first protective layer 903 and second protective layer 904 are
preferably layers including silicon such as silicon carbide (SiC),
amorphous silicon. If aluminum is used for the surface electrodes 908a
and 908b, a direct contact between the amorphous silicon and aluminum
surface electrode 908a and 908b eats away at the aluminum surface
electrodes 908a and 908b and therefore a provision of silicon carbide
(SiC) layer between the amorphous silicon and aluminum surface electrodes
908a and 908b is preferable. Alternatively, an electrode may be formed by
mixing aluminum with an impurity such as silicon, or a barrier layer may
be provided by using a material other than a SiC layer. Such a barrier
layer may comprise two or more layers.

[0157]As an example, the first insulation layer 901 and second insulation
layer 902 of FIG. 9A is one layer made from silicon dioxide (SiO2).
Meanwhile, the mirror element according to the embodiment 3 is configured
to equip the electrodes 909a, 909b and 914 so as to secure an electrical
connection to the second Vias 915a, 915b and 915c. The electrodes 909a,
909b and 914 may preferably use a high electric conductivity material
such as aluminum.

[0158]The electrode 914 at the center shown in FIG. 9A (constituting a
hinge electrode later) is an electrode equipped for an elastic hinge 911
and is configured to be the same height as that of the electrodes 909a
and 909b on the left and right. The forming of the individual electrodes
909a, 909b and 914 to be the same height between the center and the left
and right makes it possible to form the three electrodes 909a, 909b and
914 in the same one process. And a barrier layer 910 made from tantrum,
titanium and such is formed on the electrode 914 at the center. The
barrier layer 910 may be structured by two or more layers. Such the
barrier layer may comprise on the three electrodes 909a, 909b and 914.
And an appropriate modification of the height of the electrode 914 at the
center makes it possible to determine a setup of a height at the center
for placing an elastic hinge 911 described later. A setup of the height
of the elastic hinge 911 may be determined by adjusting the height of the
barrier layer 910.

[0159]Then, the elastic hinge 911 is formed on the electrode 914 at the
center, on which the barrier layer 910 is formed, so as to be connected
to the barrier layer 910.

[0160]The elastic hinge 911 is made from amorphous silicon or silicon
germanium (SiGe), for example. The thickness of the elastic hinge 911 (in
the left and right direction of the drawing of FIG. 9A) is preferably
approximately 150 to 500 angstroms.

[0161]Here, a plurality of elastic hinges may be provided for one mirror
and the mirror may be supported by individually smaller width elastic
hinges. As an example, two of an elastic hinge narrower than the
conventional configuration may be placed for one mirror at both end parts
thereof.

[0162]Meanwhile, the elastic hinge 911 preferably possesses an electric
conductivity by applying an In-Situ doping (such as arsenic and
phosphorus), an ion implanting, a diffusion of metallic silicide such as
nickel silicide (NiSi), titanium silicide (TiSi) or such. Furthermore,
the mirror element according to the embodiment 3 is configured to
accumulate a third protective layer 905 on the surface of the structure
part of the semiconductor wafer substrate on which the electrodes 909a,
909b and 914 are formed. A third protective layer 905 is preferably a
layer including silicon such as silicon carbide (SiC), amorphous silicon.

[0163]Meanwhile, the upper surface of the elastic hinge 911 may be
provided with a joinder portion, which can be configured to be the same
form and area size as the mirror 913 as described later. The embodiment 3
is configured to make the joinder portion as the smallest area size as
possible. Such a configuration makes it possible to prevent the mirror
913 from being deformed or warped by the difference of linear expansion
coefficients between the mirror 913 and joinder portion. And a metallic
layer 912 is accumulated on the joinder portion of the elastic hinge 911
for securing electric conductivity between the elastic hinge 911 and
mirror 913 while eliminating a variation of the heights among individual
mirror elements.

[0164]As an example, the metallic layer 912 is a material including
tungsten or titanium; a material including another metal may be
accumulated instead.

[0165]If the mirror 913 is made from aluminum and the elastic hinge 911 is
configured by using a silicon material, then a barrier layer (not shown
in a drawing herein) may further be layered on the metallic layer 912 in
order to prevent the mirror 913 from contacting with the joinder portion.
Such a barrier layer may be constituted by two or more layers.

[0166]The barrier layer is made from a material including tantrum,
titanium, et cetera. And the mirror element according to the embodiment 3
is structured by forming the mirror 913 on the metallic layer 912 of the
elastic hinge 911.

[0167]The mirror 913 is desirably to be made from a material with high
reflectivity of light, such as aluminum. And the mirror 913 is
approximately square, with one side thereof being preferably between 4
and 10 μm. The gap between individual mirrors 913 may preferably be
0.15 to 0.55 μm. And the aperture ratio of individual mirror element
is desirably to be designed about 90%.

[0168]Such is the configuration of the mirror element according to the
embodiment 3 shown in FIG. 9A.

[0169]FIG. 9B is a plain view diagram of a surface part of a semiconductor
wafer substrate of the mirror device according to the embodiment 3.

[0170]Note that the electrodes 909a and 909b on the left and right and the
electrode 914 at the center, which are formed on the mirror 913 and the
second Vias 915a, 915b and 915c, are delineated by the dotted lines. And
the deflection axis of the mirror 913 is indicated by the chain lines.

[0171]As shown in FIG. 9B, the second Vias 915a, 915b and 915c for
securing an electric conduction with the electrodes 909a, 909b and 914
are placed under the electrodes 909a, 909b and 914. And the surface
electrodes 908a and 908b formed in a manner to increase a coulomb force
for deflecting the mirror 913 are formed thereunder.

[0172]FIG. 9C is a plain view diagram when the mirror 913 of the mirror
device of the embodiment 3 is removed, where the mirror 913 is indicated
by the dotted lines. As shown in FIG. 9C, the respective apexes of the
electrodes 909a and 909b at both end parts of the mirror 913 are formed
as protrusion. And the design is such that the deflection angle of the
mirror 913 is at a prescribed angle when contacts with the protrusion of
the electrodes 909a and 909b when the mirror 913 is deflected.

[0173]The tips of the electrodes 909a and 909b are desirably to be
designed so as to make the deflection angle of the mirror 913 between 8
and 14 degrees. Such deflection angle of the mirror 913 is desirably to
be designed in compliance to the design of the light source and optical
system of a projection apparatus. And the length of the elastic hinge 911
of each mirror element is preferably configured to be 2 μm or shorter,
and the mirror 913 is preferably configured to be an approximate square
with the length of one side being 10 μm or smaller. FIG. 9D is a
cross-sectional diagram when the mirror element shown in FIG. 9A is
deflected to an ON state.

[0174]The embodiment 3 is assumed to be configured to reflect the light
emitted from a light source as the ON light when the mirror 913 shown in
FIG. 9A is deflected to the right side, while reflect the light emitted
from the light source as the OFF light when the mirror 913 is deflected
to the left side.

[0175]When a voltage is not applied to the individual electrode 908a or
908b on the left and right, or the individual electrode 909a or 909b, the
elastic hinge 911 is not deformed and the mirror 913 is maintained in the
horizontal direction.

[0176]Here, an application of a voltage to the right side electrode 909b
and right side surface electrode 908a generates a coulomb force
determined by:

[0177][top surface area size of electrode]*[voltage applied to
electrode]*[the second power of the distance between aluminum and
mirror],

[0178]Between the right side electrode 909b and mirror 913 and between the
right side surface electrode 908a and mirror 913. And the mirror 913 is
deflected by the total coulomb force generated between the right side
electrode 909b and mirror 913 and between the right side surface
electrode 908a and mirror 913.

[0179]In this event, the distance between the mirror 913 and right side
surface electrode 908a is longer than that between the mirror 913 and
right side electrode 909b, and the area size of the right side surface
electrode 908a is smaller than that of the right side electrode 909b, and
therefore the generated coulomb force is also smaller than that generated
between the right side electrode 909b and mirror 913. And in the state of
the mirror 913 being drawn to the right side surface electrode 908a as a
result of the mirror being deflected, the mirror 913 is deflected to 12
to 14 degrees and the reactive force of the elastic hinge due to the
resilience is now strong. The coulomb force works in a manner to draw the
tip part of the mirror 913 to the right side surface electrode 908a
placed on the substrate surface, however, so that the mirror 913 can be
drawn by a smaller coulomb force because of the principle of the lever
(that is, the principle of the moment of a rigid body. As a result, the
right side surface electrode 908a is capable of retaining the deflection
of the mirror 913 in the state of a low voltage being applied thereto.

[0180]When the mirror 913 is deflected to the right side, the surface
electrode 908b on the other side (that is, the left side) and the left
side electrode 909a are put in the same potential and grounded by
connecting to the GND.

[0181]Meanwhile, an equipment of the surface of the semiconductor wafer
substrate with the electrodes 909a and 909b and hinge electrode 914 makes
the substrate surface possess the not flat surfaces. The light projected
from the light source passes through the mirror gap reaches the electrode
and reflected again from the mirror to reduce an undesirable reflect
light.

[0182]FIG. 9E is a cross-sectional diagram when the mirror element shown
in FIG. 9A is deflected to an OFF state. In FIG. 9E, an application of a
voltage to the left side surface electrode 909a and left side electrode
908b makes it possible to deflect the mirror 913 to the left side
likewise the content noted for FIG. 9D.

[0183]The principle and the action of the Coulomb force in this case is
similar to that noted for FIG. 9D and therefore the description is
omitted here.

[0184]Incidentally, in the case of changing the forms of the mirror 913
and elastic hinge 911 on the right and left sides of the mirror element,
that of differentiating the resilience of the elastic hinge 911 on the
right and left sides of the mirror element and that of changing the
deflection control for the mirror 913 on the right and left sides of the
mirror element, the area size, height and placement (i.e., layout) of the
respective surface electrodes 908a and 908b, or the respective electrodes
909a, 909b and 914, on the right and left sides of the mirror element may
be changed so as to apply an appropriate voltage, thereby controlling the
deflection of the mirror 913.

[0185]Furthermore, a control can be performed in a manner to apply
voltages in multiple steps to the respective surface electrodes 908a and
908b and respective electrodes 909a and 909b on the right and left sides
of the mirror element.

[0186]Furthermore, the circuit and voltage for driving either one of the
surface electrodes 908a and 908b and electrodes 909a and 909b of the
surface electrodes 908a and electrode 909b on the right side of the
mirror element or the surface electrode 908b and electrode 909a on the
left side may be appropriately changed.

[0187]Furthermore, both or either one of the surface electrodes 908a and
908b and electrodes 909a and 909b of the surface electrodes 908a and
electrode 909b on the right side of the mirror element or the surface
electrode 908b and electrode 909a on the left side may be protruded from
the substrate.

[0188]Furthermore, both or either one of the surface electrodes 908a and
908b and electrodes 909a and 909b of the surface electrodes 908a and
electrode 909b on the right side of the mirror element or the surface
electrode 908b and electrode 909a on the left side may be placed on the
surface of the substrate.

[0189]As such, the mirror 913 of the mirror element according to the
embodiment 3 is deflected, thereby making it possible to change the
reflecting direction of the illumination light appropriately.

[0190]The next is a description on a production method for the mirror
device of the above described embodiments 1, 2 and 3 by referring to
FIGS. 10A through 13B. That is the production method for the mirror
device described below is that for the mirror element possessing the
characteristic of the elastic hinge or electrode described above.

<Mirror Device Production Method 1>

[0191]FIG. 10A through 13B note the production method for the mirror
device according to the present embodiments primarily shown in FIGS. 7A
and 7B; a mirror device of another embodiment can also be produced by
modifying the similar process a little.

[0192]FIGS. 10A and 10B are cross-sectional diagrams of one mirror element
of a mirror device for describing a production process of the mirror
device.

[0193]The step 1 of FIG. 10A forms, on the semiconductor wafer substrate
704, a drive circuit (not shown in a drawing herein) for driving and
controlling a mirror placed later, the address electrodes 703a and 703b
which are connected to the drive circuit and the stopper 707 for
determining the deflection angle of the mirror 701 as the stopper 707
contacts the mirror and prevents the mirror from moving beyond a
predefined angle. Then the process proceeds with a step of confirming the
operation of the drive circuit and a presence or absence of the
electrical connection of the address electrodes 703a and 703b. If there
is no abnormality in the drive circuit or address electrodes 703a and
703b, the process proceeds to a step 2.

[0194]The step 2 of FIG. 10A accumulates the first sacrifice layer 1001 of
a height approximately desired as the elastic hinges 702a and 702b on the
semiconductor wafer substrate 704 on which the drive circuit (not shown
in a drawing herein), address electrodes 703a and 703b and stopper 707
have been formed. The first sacrifice layer 1001 is used for forming the
mirror surface to be formed in a later step by maintaining a gap against
the semiconductor wafer substrate 704. In the present embodiment, the
height of the first sacrifice layer 1001 results in determines the height
of the elastic hinges 702a and 702b, described later, supporting the
mirror 701.

[0195]The first sacrifice layer 1001 according to the present embodiment
is accumulated on the semiconductor wafer substrate 704, address
electrodes 703a and 703b and stopper 707 by using the method called a
chemical vapor deposition (CVD). The chemical vapor deposition is a
method for placing a semiconductor wafer in a reaction chamber, supplying
a material in accordance with the kind of sacrifice layer in a gas state
and accumulating a film by utilizing a chemical catalytic reaction.
Plasma Enhanced CVD (PECVD) is more preferable. The sacrifice layer 1001
preferably uses a material such as tetraethoxysilane (TEOS).

[0196]The step 3 of FIG. 10A removes the first sacrifice layer 1001 by
applying the etching and equipping an opening part for determining the
height and form of the elastic hinges 702a and 702b to be formed in a
later process. The opening part is preferably as small as possible for
widening the spots for placing the address electrodes 703a and 703b. The
present embodiment is configured to equip the opening part nearby the
deflection axis on the end part of the mirror 701.

[0197]FIG. 11A is a plain view diagram of the mirror element viewing from
the arrow direction III of FIG. 10A in the step 3. FIG. 11A shows a part
of the mirror element covered with the first sacrifice layer 1001 and the
mirror 701 to be formed later by the dotted lines. An opening part is
formed nearby the deflection axis on the end part of the mirror 701 for
generating the elastic hinges 702a and 702b. FIG. 11A shows the forming
of the opening part 1005a to the right of the deflection axis in the
upper end part of the mirror 701, and of the opening part 1005b to the
left of the deflection axis in the lower end part of the mirror 701. This
configuration is for placing the address electrodes 703a and 703b
symmetrically about a point of the center of the mirror 701, thereby
equalizing the area sizes of the address electrodes 703a and 703b on the
left and right sides of the deflection axis as noted for FIG. 7A. And the
width (i.e., the up and down direction, of the drawing, of the opening
part) of the opening parts 1005a and 1005b is preferably to be so formed
as to be equivalent to the width of a desired width of the elastic hinges
702a and 702b. If two of the elastic hinges 702a and 702b are formed as
shown in FIG. 7A, the width of the respective elastic hinges 702a and
702b may be reduced to half of the width of the elastic hinge at the time
of supporting one mirror with one elastic hinge. Meanwhile, the
individual opening parts may be formed for forming an elastic hinge by
using the opening part on the upper end part of the mirror and the
opening part on the lower end part of the adjacent mirror so as to share
one elastic hinge by mutually adjacent mirrors likewise the elastic hinge
as noted in FIG. 6.

[0198]The step 4 of FIG. 10A accumulates the joinder portion 702 on the
first sacrifice layer 1001 and opening parts 1005a and 1005b. FIG. 10A
shows the elastic hinges 702a and 702b and the joinder portion 702 as one
body. Preferable materials may include amorphous silicon, poly-silicon or
such for example. In the present embodiment, the joinder portion 702, the
elastic hinges 702a and 702b for supporting the mirror 701 are formed by
a later application of an etching. The thickness of the joinder portion
702 covering the opening parts 1005a and 1005b eventually determines the
thickness of the elastic hinges 702a and 702b.

[0199]The step 6 of FIG. 10A accumulates a first mask layer 1002 on the
joinder portion 702. The first mask layer 1002 is a photoresist for
example.

[0200]The step 6 of FIG. 10A applies a patterning to the first mask layer
1002. The first mask layer 1002 by using a mask for obtains the desired
structural body feature of the joinder portion 702, the elastic hinges
702a and 702b. In specific, the etching is employed to remove the joinder
portion 702 by leaving a part of the elastic hinges 702a and 702b on
which the first mask layer 1002 has been accumulated and the first mask
layer 1002 as shown in the present step for example. In the case of the
present embodiment, the joinder portion 702, the elastic hinges 702a and
702b are integrated together. The drawing of the present step shows how a
space is created in a part of the opening parts 1005a and 1005b as a
result of etching the part of the opening parts 1005a and 1005b in order
to obtain a desired structural body feature.

[0201]FIG. 11B is a plain view diagram of the mirror element viewing from
the arrow direction IV of FIG. 10A in the step 6. (The first mask layer
1002 is not shown in a drawing herein)

[0202]FIG. 11B shows a part of the mirror element and the dotted lines
shows the locations provided for mirror 701 to be formed later. FIG. 11B
also shows the part exposing the joinder portion 702 and the elastic
hinges 702a and 702b by the solid lines. The joinder portion is formed on
the two elastic hinges 702a and 702b. An etching is applied in a desired
form so that the joinder portion 702 is connected to the two elastic
hinges 702a and 702b. Such connection of the two elastic hinges 702a and
702b in the same joinder portion 702 makes it possible to suppress a
deformation of the elastic hinges 702a and 702b. Also, if an external
force is applied, the force is distributed by the joinder portion 702 to
prevent the force from being applied to directly the elastic hinges 702a
and 702b, making them hard to break.

[0203]Meanwhile, the end part of the mirror 701 where the joinder portion
702 does not exist allows a step in nanometer order of a wavelength of
light when the mirror is accumulated as noted for FIG. 7B. Therefore, a
step is formed on the end part of the mirror 701 in the direction of
incident light in a completed mirror 701. Then, the diffraction light of
the incident light is generated in the arrow direction shown in FIG. 7B
due to the step on the end part of the mirror 701. In the case of the
mirror 302 of which a joinder portion does not exist and the elastic
hinge is formed at the center of the mirror 302 as shown in FIG. 5,
however, a concave or convex step 552 is generated at the center of the
mirror 302. And the diffraction light 553 of the incident light from the
step of the center part of the mirror 302 is generated in the arrow
direction shown in FIG. 5. Comparing these cases, the diffraction light
generated in a narrow range (i.e., the range of half the width of the
elastic hinge) based on the width of the elastic hinges 702a and 702b on
the end parts of the mirror 701 shown in FIG. 7B is harder to be incident
to the projection lens than the diffraction light generated from the
concave or convex step 552 on the center of the mirror 302 shown in FIG.
5. Because of this, a degradation of the contrast of an image due to the
diffraction light can be prevented.

[0204]The step 7 of FIG. 10B further accumulates a second sacrifice layer
1003 on the structural body formed on the semiconductor wafer substrate.
A part of the space of the etched opening part is filled with the second
sacrifice layer 1003. Then, the accumulated the second sacrifice layer
1003 is polished to the extent of exposing the surface of the joinder
portion 702.

[0205]The step 8 of FIG. 10B accumulates a support layer 706 of the mirror
701 on the top surfaces of the exposed elastic hinges 702a and 702b and
joinder portion 702. The support layer 706 is furnished between the
mirror 701 and elastic hinges 702a and 702b for reinforcing the
conjunction of the mirror layer 710 with the elastic hinge 702 supporting
the mirror layer 701, or for preventing a stiction of the mirror onto the
stopper 707 contacting the mirror (i.e., the mirror layer) 701 at the
time of the mirror deflecting. The support layer 706 may preferably use a
material such as titanium, tungsten or the like.

[0206]The step 9 of FIG. 10B accumulates the mirror layer 701 on the
support layer 706. Note that another layer (such as a barrier layer) may
further be provided prior to forming the mirror layer 701. The mirror
layer 701 according to the present embodiment is configured to use a
material with good reflectivity, such as aluminum, gold, silver and the
like.

[0207]The step 10 of FIG. 10B further accumulates a second mask layer 1004
on the structural body formed on the semiconductor wafer substrate. The
second mask layer 1004 may also be a photoresist for example.

[0208]The step 11 of FIG. 10B applies an exposure of a mirror pattern by
using a mask for the photoresist that is the second mask layer 1004 for
example. It is followed by etching the second mask layer 1004, mirror
layer 701 and support layer 706 in accordance with the mirror pattern,
separating the mirror layer 701 and support layer 706 into individual
mirrors 701 and forming the feature of one mirror 701. In specific, gaps
are furnished between the mirrors 701 so that the adjacent mirrors 701 do
not contact with each other and also the mirror surface of the mirror 701
is formed into a desired feature.

[0209]The step 12 of FIG. 10B removes the first sacrifice layer 1001 by
using an etchant. The above described processes enable the drive circuit
(not shown in a drawing herein) and address electrodes 703a and 703b to
deflect the elastic hinges 702a and 702b and mirror 701 which are formed
on the semiconductor wafer substrate 704. The actual production process
includes a process (i.e., a dicing process) for dividing the mirror
device into mirror devices of a usage size, a process for packaging the
individually divided mirror devices, an anti-stiction countermeasure
process for preventing from the moving parts (mainly mirrors) from
sticking to another member (such as the mirror stopper) and becoming
inoperable, and other processes; the description is omitted here,
however.

[0210]The production method as described above makes it possible to
configure the mirror device according to the present embodiment. Note
that the mirror device is preferably to be produced by configuring the
elastic hinges 702a and 702b of each mirror element to have the length of
2 μm or smaller and the mirror 701 of each mirror element to be an
approximate square with one side of 5 μm to 10 μm.

<Mirror Device Production Method 2>

[0211]FIGS. 12A through 13B illustrate steps implemented by a production
method for a mirror device according to the present embodiment.

[0212]This also is applicable to the production method for the mirror
devices noted in the embodiments 1, 2 and 3 by applying various changes
to a similar process.

[0213]FIGS. 12A through 12C are cross-sectional diagrams of one mirror
element of a mirror device comprising two million mirror elements for
describing a production process of the mirror device.

[0214]The step 21 of FIG. 12A forms the wiring 1205 of a drive circuit for
driving and controlling a mirror to be formed later, a first Via 1206
connected to the drive circuit and a second insulation layer 1202 on a
first insulation layer in the semiconductor wafer substrate. The
processes proceed with processes of forming a second via 1207 on the
first via 1206, and forming a first protective layer 1203 and a second
protective layer 1204 on the second insulation layer 1202.

[0215]The wiring of the drive circuit is preferably an aluminum wiring.

[0216]The first via 1206 and second via 1207 are preferably to be
constituted by a metal including tungsten and cupper.

[0217]Each of the first insulation layer 1201 and second insulating layer
1201 is preferably silicon dioxide (SiO2).

[0218]Each of the first protective layer 1203 and second protective layer
1204 is preferably a layer including silicon such as silicon carbide
(SiC), amorphous silicon. The present step accumulates silicon dioxide
(SiO2) as the insulation layer; silicon carbide (SiC) as the first
protective layer 1203; and amorphous silicon as the second protective
layer 1204. Here, the thickness of 300 to 1000 angstroms of the silicon
carbide (SiC) is accumulated for the first protective layer 1203 and that
of 1000 to 3000 angstroms of the amorphous silicon is accumulated for the
second protective layer 1204. These layers are for preventing hydrogen
fluoride (HF) from corroding the first via 1206; second via 1207 when HF
is applied to remove the sacrifice layers in a later process.

[0219]An alternative process for securing the electrical connection with
the electrodes 1208a, 1208b and 1209 may be to accumulate the first
protective layer 1203 and second protective layer 1204 first on the first
insulation layer 1202 and put holes in the respective protective layers
1202 and 1204, followed by accumulating the second Via 1207. If aluminum
is used for the electrodes 1208a, 1208b and 1209, a direct contact
between the amorphous silicon and the aluminum-made electrodes 1208a,
1208b and 1209 results in corrosion of the aluminum electrodes and
therefore an equipment of a silicon carbide (SiC) layer between the
amorphous silicon and aluminum electrodes is recommended. On the other
hand, a forming of the electrodes 1208a, 1208b and 1209 by mixing an
impurity, such as silicon, with aluminum, or a provision of a barrier
layer using a material other than a SiC layer may be appropriate.

[0220]The step 22 of FIG. 12A equips the structural body on the
semiconductor wafer substrate with the electrodes 1208a, 1208b and 1209
so as to be electrically conductive with the second via 1207.

[0221]The electrodes 1208a, 1208b and 1209 are preferably to be
constituted by aluminum for example. The center electrode 1209 (becoming
a hinge electrode later) of the present step is an electrode equipped for
the elastic hinge and is configured to be the same height as that of the
left and right electrodes. The forming of the individual electrodes
1208a, 1208b and 1209 by configuring the same height between the center
electrode 1209 and the left and right electrodes 1208a and 1208b as such
makes it possible to form the three electrodes 1208a, 1208b and 1209 in
the same process. Or it is possible to change the height of the
electrodes. Then, a barrier layer 1210, made from tantrum, titanium or
the like, is formed on the center electrode 1209. The barrier layer 1210
may comprise two or more layers.

[0222]Meanwhile, an appropriate adjustment of the height of the center
electrode 1209 makes it possible to determine a setup of the height of
the elastic hinge as described later. A setup of the height of the
elastic hinge may be determined by adjusting the height of the barrier
layer 1210.

[0223]The step 23 of FIG. 12A forms a third protective layer 1211 on the
structural body of the semiconductor wafer substrate on which the three
electrodes 1208a, 1208b and 1209 have been formed and forms a forth
protective layer 1212 on the third protective layer 1211.

[0224]The third protective layer 1211 and fourth protective layer 1212 are
preferably layers including silicon such as silicon carbide (SiC),
amorphous silicon. The present step accumulates silicon carbide (SiC) as
the third protective layer 1211 and amorphous silicon as the
forth-protective layer 1212. Likewise the content noted for the step 21,
in the case of the electrodes 1208a, 1208b and 1209 being constituted by
aluminum, these layers are formed for prevention of corrosion of the HF
that is used in a later process.

[0225]The step 24 of FIG. 12A accumulates a sacrifice layer 1213 on the
structural body of the semiconductor wafer substrate on which the forth
protective layer 1212 is formed on the third protective layer 1211. It is
followed by etching the part of the accumulated third protective layer
1211, forth protective layer 1212 and sacrifice layer 1213, in which the
elastic hinge is to be formed, to form a hole.

[0227]The present embodiment is configured to put a hole on the center
electrode on which an elastic hinge is to be formed. The depth of the
hole is determined by the thickness and width of the elastic hinge and by
the deflection angle of the mirror. The depth of the hole is preferably
to be 0.4 to 1.2 μm. The depth is able to be shallow compare with step
3 of FIG. 10A and yield of production of the elastic hinge is
improvement.

[0228]The step 25 of FIG. 12B forms the sacrifice layer 1213 and
accumulates a hinge layer 1214, which becomes an elastic hinge, on the
structural body of the semiconductor wafer substrate of which the hole is
put for forming the elastic hinge. The hinge layer 1214 is an amorphous
silicon layer or silicon germanium for example.

[0229]The hinge layer 1214 is accumulated by making the top surface of the
sacrifice layer 1213 using a polishing process. The thickness of the
hinge layer 1214 is preferably between 150 and 350 angstroms. The
thickness is able to be thin compare with step 4 of FIG. 10A and
manufacturing process period of accumulates a hinge layer 1214 is able to
reduce.

[0230]Meanwhile, the hinge layer 1214 formed on the surface of the hole is
preferably to possess an electric conductivity by applying an In-Situ
doping (such as arsenic and phosphorus), an ion implanting, a diffusion
of metallic silicide such as nickel silicide (NiSi), titanium silicide
(TiSi) or such.

[0231]The step 26 of FIG. 12B forms a desired feature of the elastic hinge
by etching the hinge layer 1214. The mask used for applying the etching
is equipped so as to fill the inside of the hole. The elastic force of
the elastic hinge 1214 is determined on the basis of the length L of the
elastic hinge, the thickness H thereof and the width W thereof.

[0232]FIG. 13A is a plain view diagram of a mirror element viewing from
the arrow direction XXVI of FIG. 12B in the step 26.

[0233]The elastic hinge is formed in a hole 1300 provided in the sacrifice
layer 1213. A part 1214upward of the elastic hinge left on the
sacrifice layer 1213 is joined with the bottom surface of the mirror by
way of several layers later. Contrarily, a part 1214downward of the
elastic hinge within the hole 1300 under the sacrifice layer 1213 is
joined with a later described barrier layer to be formed on the
structural body of the semiconductor wafer substrate.

[0234]When the elastic hinge 1214 is formed, variations of the thickness
and length of the elastic hinge 1214 for individual mirror elements
influence greatly the elastic strength.

[0235]Moreover, there is a possibility of the elastic hinge being deformed
after removing the sacrifice layer 1213 due to a residual stress, which
has been left at the time of production. Therefore, the elastic hinge is
desirably to be formed so as to satisfy the condition of [width W of
elastic hinge>length L of elastic hinge]. Particularly, the elastic
hinge 1214 is desirably to be standing approximately vertical between the
mirror 1217 and the center electrode 1209 and satisfy the relationship of
[width of elastic hinge≧length of elastic hinge>thickness of
elastic hinge].

[0236]In an experiment by setting the length L of the elastic hinge to 1
μm and the width W thereof to 1.2 μm, confirmed is the fact of a
mirror 1217 layered on the elastic hinge 1214 being well stabilized.

[0237]Here, an alternative configuration may be such that a plurality of
elastic hinge is placed for one mirror, with the width W of each elastic
hinge being smaller for supporting the mirror. As an example, two elastic
hinge of a smaller width than the conventional elastic hinge may be
placed at both end parts of one mirror as shown in FIG. 8.

[0238]The top surface of the elastic hinge may be equipped with a joinder
portion which can be configured to be an area size and/or form similar to
those of a later described mirror. The present embodiment is configured
to make the joinder portion as small an area size as possible. Such a
configuration makes it possible to prevent the mirror from being deformed
or warped due to the difference of linear thermal expansion between the
mirror and joinder portion. The step 27 of FIG. 12B further accumulates a
mask layer 1215 on the structural body of the semiconductor wafer
substrate which is formed in a desired feature of the elastic hinge 1214.

[0239]The mask layer 1215 is accumulated in a manner to completely cover
the joinder portion of the elastic hinge 1214 so as to fill the hole
formed for the elastic hinge 1214 and maintain an electrical connection
between the elastic hinge and a mirror layer 1217 described later. The
mask layer 1215 may use a material such as a photoresist.

[0240]The step 28 of FIG. 12B applies a mask layer 1215 of the structural
body of the semiconductor wafer substrate on which the mask layer 1215 is
formed so as to accumulate a metallic layer 1216 on the joinder portion
of the elastic hinge 1214. The process continues with a process of
further accumulating a few layers on the joinder portion. In the present
step, if the size of the semiconductor wafer substrate is eight inches of
diameter, the polishing is preferably carried out in a manner to expose
the joinder portion of the elastic hinge 1214 of the respective mirror
elements both of which formed on nearby the center part of the
semiconductor wafer substrate and the ones formed nearby the end parts
thereof.

[0241]Even with such a polishing being carrier out, the area sizes and/or
height of the parts exposing the joinder portion of the elastic hinge
1214 are actually different between the mirror elements formed nearby the
center part of the semiconductor wafer substrate and the ones formed
nearby the end parts thereof. In order to eliminate the variation of the
height among the individual mirror elements on one hand and secure an
electrical connection between the elastic hinge 1214 and mirror 1217 on
the other, the metallic layer 1216.

[0242]As an example, the metallic layer 1216 is a material including
tungsten or titanium; alternatively however, a material including other
metal may be accumulated.

[0243]If the mirror 1217 is formed by aluminum and if the elastic hinge
1214 is formed by using a silicon material, a barrier layer (not shown in
a drawing herein) further layered on top of, and under, the metallic
layer 1216 so as not to allow the mirror 1217 to contact with the elastic
hinge 1214. Note that the barrier layer may be constituted by two or more
layers.

[0244]The step 29 of FIG. 12C accumulates the mirror layer 1217 on the
structural body of the semiconductor wafer substrate. It is followed by
applying an etching to the accumulated mirror layer 1217 for forming a
desired feature of the mirror. The mirror layer 1217 is preferably to be
formed by a material with high reflectivity of light, such as aluminum.

[0245]The present embodiment applies the etching so as to form the
individual mirrors in approximate square. One side of the approximate
square mirror is desirably between 4 and 10 μm. Further preferably to
have the gap of between 0.15 and 0.55 μm between individual mirrors.
And the aperture ratio of each mirror element is desirably to be designed
about 90%. The etching is followed by layering a protective layer (not
shown in a drawing herein) on the entire surface of the structural body
on the semiconductor wafer substrate on which the mirror layer has been
formed. The protective layer used in this event is the TEOS for example.

[0246]It is followed by dicing the mirror element into two-million mirror
elements. The aforementioned protective layer is formed for protecting
the mirror elements during the dicing.

[0247]It is followed by dividing the semiconductor wafer substrate into an
individual mirror array on which the two million mirror or more elements
have been formed.

[0248]The step 30 of FIG. 12C removes the sacrifice layer of the
structural body of the semiconductor wafer substrate on which the mirror
layer has been formed. If the sacrifice layer is formed with the TEOS,
the sacrifice layer is removed by using hydrogen fluoride (HF) and
alcohol. An appropriate adjustment of the hydrogen fluoride (HF) and
alcohol and the processing time makes it possible to remove the sacrifice
layer and residual foreign materials completely. Such a process makes it
possible to form an anti-stiction layer on the forth-protective layer
1212 after a dicing process.

[0249]FIG. 13B shows the elastic hinge 1214 and mirror 1217 constituted on
the center electrode 1209 of the mirror element of the mirror device
formed in the production processes shown in FIGS. 12A through 12C.

[0250]The barrier layer 1210 is overlaid on the center electrode 1209 on
the semiconductor wafer substrate and the barrier layer 1210 is joined
with the elastic hinge 1214. The third protective layer 1211 is overlaid
on the center electrode 1210 and the forth-protective layer 1212 is
further overlaid on the third protective layer 1211.

[0251]And the upper joinder part of the elastic hinge 1214, and a barrier
layer 1218 is formed on the joinder part. And a metallic layer 1216 is
overlaid on the barrier layer 1218, and a barrier layer 1220 is further
overlaid on the metallic layer 1216. That is, the top and bottom surface
of the metallic layer 1216 is covered with the barrier layers 1220 and
1218, respectively. The barrier layers 1220 and 1218 are connected to the
mirror layer 1217. Note that an appropriate adjustment of the joinder
part, metallic layer 1216 or barrier layers 1220 and 1218 formed on the
top and bottom surfaces of the metallic layer 1216 makes it possible to
correct the height for forming the mirror layer 1217. As such, the mirror
1217 is supported by the elastic hinge 1214 formed on the center
electrode 1209 of the mirror element, which is produced by the production
method according to the present embodiment.

[0252]The amorphous silicon of the elastic hinge 1214 is layered by
employing the chemical vapor deposition (CVD). In this event, the
amorphous silicon layer is formed in a manner to make the thickness to be
the smallest in the root part HL of the elastic hinge, increasing the
thickness gradually in the center upper part HU of the elastic hinge and
the largest in the joining part HP with the joinder layer of the elastic
hinge. That is, in the end part of the elastic hinge 1214 close to the
center electrode 1209 and the and part of the elastic hinge 1214 close to
the mirror 1217, the following relationship is desirably to be satisfied:

[0253][Cross-sectional area size of end part of elastic hinge close to
electrode]≦[cross-sectional area size of end part of elastic hinge
close to mirror];

[0254]An experiment of such an elastic hinge 1214 including silicon has
confirmed the fact of the durability being very high as an elastic body
and the elastic hinge 1214 not being broken even after the deflection
cycles thereof reaching at trillions of times. As such, the mirror
element produced by the production method noted in the present
specification document is well capable of enduring in an actual usage.
Note that the mirror device is preferably to be produced by configuring
the length of the elastic hinge 1214 of each mirror element to be 2 μm
or smaller and the mirror 1217 of each mirror element to be an
approximate square with one side of 10 μm or smaller. Also note that a
comprisal of the electrodes 1208a, 1208b and hinge electrode 1210 on the
substrate surface makes it possess the convex and concave surfaces.

[0255]The next is a description of projection apparatuses comprising
mirror devices according to the embodiments 1, 2 and 3. The projection
apparatuses include a single-plate projection apparatus and a multi-plate
projection apparatus, and the mirror devices according to the embodiments
1, 2 and 3 are applicable to both of the projection apparatuses.

<Single-Plate Projection Apparatus>

[0256]Described here is an example of a single-plate projection apparatus
comprising a single mirror device put forth in the present embodiment.

[0257]FIG. 14 is a configuration diagram of a single-plate projection
apparatus comprising a mirror device according to the present embodiment.

[0259]A light source 401 emits the light for projecting an image. The
light source 401 is controlled by a light source control unit 402
comprised by a processor 410. The light source 401 may be an arc lamp
light source, a laser light source or a light emitting diode (LED). The
light source 401 may even be constituted by a plurality of sub-light
sources. The number of the sub-light sources to be lit is controlled by a
light source control unit 402, thereby adjusting the light intensity.
Also, the light source control unit 402 biasing the position of the
sub-light sources to be lit makes it possible to bring forth a locality
of the light intensity.

[0260]If the light source 401 is constituted by a plurality of laser light
sources with different wavelengths, the light source control unit 402
changing over among the individual laser light sources enables a
selection of a color of incident light. Therefore, this configuration
does not require a color wheel 406 described later. Also it is possible
to carry out a pulse emission of light of a laser light source or of
light emitting diode (LED) light source.

[0261]When using a near-parallel flux of light with a small light
dispersion angle, such as a laser light source, the numerical aperture NA
of an illumination light flux and of the flux reflecting on the mirror
device 414 can be reduced based on the relationship of etendue. By this,
while avoiding an interference of the illumination light flux prior to
being reflected on the mirror device 414 with the projection light flux
after being reflected thereon, these fluxes can be moved close to each
other. As a result, the mirror can be downsized and also the deflection
angle of the mirror can be smaller. And the making of the deflection
angle of mirror smaller by moving the illumination light flux and
projection light flux closer to each other makes it possible to shorten
the difference of light path lengths between the incident light and
reflection light passing through a package 413 and make the difference of
a rate of light transmission of the package 413 smaller. That is, larger
light quantity of incident light and reflection light enter the mirror
array and projection path. Therefore, making the deflection angle of the
mirror small by using a laser light source enables a projection of a
brighter image.

[0262]A condenser lens-1 403 converges the light from the light source
401. A rod integrator 404 uniforms an intensity of light. A condenser
lens-2 405 converges the light emitted from the rod integrator 404. A
color wheel 406 is constituted by a filter member, which is constituted
by a plurality of filters. Each of the individual filters extracts a
specific wavelength. As an example, the filter member can be constituted
by three filters, i.e., a filter for extracting the light of the
wavelength of red, one for extracting the light of the wavelength of
green and one for extracting the light of the wavelength of blue. And,
each filter of a light-passing path can be changed over by a color wheel
drive unit 407 so as to rotate or slide the filter member constituted by
the filters. The filter may have a characteristic of polarization. A
motor control unit 408 of the processor 410 controls the color wheel
drive unit 407. The rotation or slide speeds of the filter are controlled
by the color wheel drive unit 407.

[0263]A total internal reflection (TIR) prism 409 is constituted by two
triangle prisms, i.e., a first prism 411 and a second prism 412. The
first prism 411 has the role of totally reflecting the incident light. As
an example, the first prism 411 totally reflects the incident light to
the light path entering the mirror device. The totally reflected light is
modulated by the mirror device and reflected to the second prism 412. The
second prism 412 transmits the reflection light which is incident thereto
at an angle smaller than a critical angle and which is modulated by the
mirror device. The mirror device 414 is housed in a package 413. The
mirror device 414 is controlled by a spatial light modulator (SLM)
control unit 415 of the processor 410.

[0264]A projection lens 416 has the role of enlarging the light reflected
and modulated by the Mirror device 414 so as to project the light on a
screen 417.

[0265]The processor 410, comprising a light source control unit 402, a
motor control unit 408 and an SLM control unit 415, is capable of
synchronously controlling each of the aforementioned control units by
combining them. The processor 410, being connected to an image signal
input unit 418, processes image signal data input therefrom. The
processor 410, further being connected to the frame memory 419, is
capable of transmitting the processed image signal data. The image signal
input unit 418 inputs the received image signal data to the processor
410. And the frame memory 419 is capable of accumulating the image signal
data of a single screen processed by the processor 410. Such is the
constituent members comprised by the single-plate projection apparatus
400 shown in FIG. 14.

[0266]The next is a description of the principle of projecting a color
image at the single-plate projection apparatus 400 shown in FIG. 14.

[0267]In the single-plate projection apparatus 400, the light emitted from
the light source 401 enters a filter of the color wheel 406 by way of the
condenser lens-1 403; rod integrator 404 and condenser lend 405. The
light of a result of extracting only the light of a specific wavelength
by a filter of the color wheel 406 enters the first prism 411 of the TIR
prism 409. And the light reflected by the first prism 411 of the TIR
prism 409 enters the mirror device 414 housed in the package 413. The
light reflected on, and modulated by, the mirror element of the mirror
device 414 re-enters the TIR prism 409 and transmits itself through the
second prism 412 thereof. Then the transmitted light is projected on the
screen 417 by way of the projection lens 416.

[0268]When projecting an image as such, the light source control unit 402
at the processor 410 controls the quantity of light, or such, of the
light source based on the image signal data receiving by way of the image
signal input unit 418. The motor control unit 408 is controlled based on
the image signal data, and the motor control unit 408 controls the color
wheel drive unit 407. And, such as a control for changing over filters of
the color wheel 406 is controlled by the color wheel drive unit 407.
Furthermore, the SLM control unit 415 controls such as a plurality of
light modulation elements of the mirror device 414 based on the image
signal data.

[0269]The single-plate projection apparatus 400 configured as described
above divides a period for displaying one image (i.e., one frame) into
sub-frames corresponding to the individual wavelengths of light in
relation to the respective wavelengths of light, e.g., a wavelength
corresponding to red, one corresponding to green and one corresponding to
blue. And the light of each wavelength is illuminated onto the mirror
device 414 in accordance with a period of each sub-frame. In this event,
the period of each sub-frame, the period of modulating the light of each
wavelength at the mirror device 414 and the period of stopping a filter
of the color wheel 406 are mutually dependent. A selective reflection of
the incident light at the mirror device 414 enables only the light of the
individual wavelength reflected to the projection light to be projected
onto the screen. And a sequential projection of lights of the individual
wavelengths in accordance with the respective sub-frame periods enables a
projection of a color image.

[0270]The next is a description of an example of a multi-plate projection
apparatus comprising a plurality of mirror devices according to the
present embodiment.

[0271]The multi-plate projection apparatus comprises a plurality of light
sources, a plurality of mirror devices and a projection lens.

[0272]The light source may preferably be a laser light source or a light
emitting diode (LED). A plurality of laser light sources may be equipped,
with each light source being independently controlled. The independent
control of each light source eliminates a necessity of a color filter by
turning on/off a laser light source having a prescribed wavelength. The
use of a laser light source enables a pulse emission, which has been
difficult to achieve with a mercury lamp.

[0273]The next is a description of the configuration and principle of a
two-plate projection apparatus, and a three-plate projection apparatus,
as examples of multi-plate projection apparatus comprising mirror devices
according to the present embodiment.

<Two-Plate Projection Apparatus>

[0274]The two-plate projection apparatus is configured to make two mirror
devices respond to two groups of light sources, respectively. And one
mirror device modulates the light from one group of light source and
another mirror device modulates the light from another group of light
source. Then, the reflected and modulated light by each of the mirror
devices is synthesized, thereby projecting an image.

[0275]As an example, when projecting an image with the lights of
wavelengths corresponding to three colors, i.e., red light, green light
and blue light, the high visibility green light is modulated by one
mirror device, and red or blue lights is modulated by another mirror
device in sequence or simultaneously, followed by synthesizing the light
modulated by each mirror device and projecting an image.

[0276]FIGS. 15A through 15D are configuration diagrams of a two-plate
projection apparatus comprising two of a mirror device, according to the
present embodiment, housed in one package.

[0278]The next is a description of the constituent components of the
projection apparatus 500 shown in FIGS. 15A through 15D.

[0279]The individual light sources 501, 502 and 503 are laser light
sources as described for the single-plate system and capable of
performing a pulse emission. They may be alternatively constituted by a
plurality of sub-laser light sources. The light source may use two
mercury lamps corresponding to the respective mirror devices. In the case
of using the mercury lamps, an equipment of a filter 505 allowing a
passage of only a light of a specific wavelength while reflecting other
light of wavelengths on the surface of synthesizing the reflection light
in a prism 510 described later provides a similar effect as a color
filter. Alternatively, a wavelength of light may be separated by using a
dichroic prism or dichroic mirror, thereby illuminating the mirror device
with the light of the separated wavelength.

[0280]The illumination optical systems 504a and 504b are optical elements
such as collector lenses described for the single-plate projection
apparatus, and rod integrators, convex lenses or concave lenses.

[0281]The prism 510 of a result of combining two triangle prisms 506 and
509 has the role of synthesizing the reflection lights from the two
mirror devices 520 and 530. When the prism 510 synthesizes the reflection
lights from the individual mirror devices, it may be appropriate to equip
the filter 505, such as dichroic filter, allowing a passage of only the
light of a specific wavelength while reflecting the other light of
wavelengths on the surface of synthesizing the reflection light in a
prism 510.

[0282]The filter 505 has the same role as a color filter because of a
capability of allowing a passage of only the light of a specific
wavelength while reflecting the other light of wavelengths. Meanwhile,
when using a laser light source emitting the light having a specific
polarization direction, a polarization light beam splitter film
separating/synthesizing light by using a difference of polarization
direction of light on the surface of synthesizing a reflection light in
the prism 510 may be used, or a polarization light beam splitter coating
may be applied to the aforementioned surface.

[0283]The package 511 is similar to the package, which has been described
for the single-plate projection apparatus. The package 511 noted in FIGS.
15A through 15D is configured to be capable of housing two mirror devices
520 and 530 within one package 511. The mirror devices 520 and 530 may be
housed in separate packages, however. Note that FIGS. 15A through 15D
show the mirror arrays 521 and 531, and device substrates 522 and 532, of
the respective mirror devices 520 and 530.

[0284]The circuit board 508 is connected to a processor similar to the one
described for the single-plate projection apparatus described above. The
processor comprises a SLM control unit and a light source control unit.
And the processor processes the input image signal data and transmits the
processed information to the SLM control unit and light source control
unit. The SLM control unit and light source control unit control the
mirror device and light source by way of the circuit board 508 based on
the processed information. The control of the mirror device can be
synchronized with that of the light source. The input of the image signal
data to the processor and other activity have been described for the
single-plate projection apparatus and therefore the description is
omitted here.

[0285]The joint member 512 has the role of joining the prism 510 to the
package 511. A material used for the joint member 512 includes a fitted
glass for example. The light shield member 513 has the role of shielding
unnecessary light. A material used for the light shield member 513
includes graphite for example. The projection apparatus 500 shown in
FIGS. 15A through 15D is equipped with the light shield member 513 not
only on a part of the bottom of the prism 510 but also on the back of the
prism 510.

[0286]The light guide prism 514 is a prism of a right-angle triangle cone
of a result of adhesively attaching the slope face on the front face of
the prism 510 with the bottom of the light guide prism 514 facing upward.
And the light guide prism 514 is equipped so that the individual light
sources 501, 502 and 503, the illumination optical systems 504a and 504b
corresponding to the respective light sources and the light axis of the
light emitted from the individual light sources 501, 502 and 503 are
respectively perpendicular to the bottom of the light guide prism 514.
This configuration enables the lights emitted from the individual light
sources 501, 502 and 503 to be orthogonal incident to the light guide
prism 514 and prism 510. This results in increasing the rate of light
transmission of the light on the incidence surface of the light guide
prism 514 and prism 510 when the respective lights emitted from the
individual light sources 501, 502 and 503 enters the light guide prism
514 and prism 510.

[0287]The projection optical system 523 is an optical element for
projecting an appropriate image onto the screen. As an example, members
such as a projection lens enlarging the light for projecting an image
onto the screen is included. Note that, when using both of a light source
emitting a polarized light and a polarization beam splitter film, a
two-plate projection apparatus can be configured by comprising a 1/2
wavelength plate or 1/4 wavelength plate on the bottom surface of the
prism 510. Such is the constituent members comprised by the two-plate
projection apparatus 500 shown in FIGS. 15A through 15D.

[0288]The next is a description on the principle of projection at the
two-plate projection apparatus 500 by referring to FIGS. 15A through 15D.

[0289]The projection apparatus 500 lets the green laser light 515 incident
from the front direction of the prism 510, followed by letting the red
laser light 516 or blue laser light 517 sequentially in a time division
and making the green laser light 515 and red laser light 516 or blue
laser light 517 be reflected to the inclined surface direction of the
prism 510 by means of the two mirror devices 520 and 530 of the present
embodiment. Then the green laser light 515 and the red laser light 516 or
blue laser light 517 which are reflected on the inclined surface side of
the prism 510 are synthesized and the image is projected on the screen by
way of the projection optical system 523.

[0290]FIG. 15A is a front view diagram of a configuration of a two-plate
projection apparatus comprising two mirror devices according to the
present embodiment.

[0291]The next is a description of the principle of projection between the
incidence of the individual laser lights 515, 516 and 517 from the front
direction of the prism 510 and the reflection of the respective laser
lights 515, 516 and 517 to the inclined surface direction of the prism
510 by means of the two mirror devices 520 and 530 by referring to the
front view diagram of the two-plate projection apparatus 500 shown in
FIG. 15A.

[0292]The green laser light 515 and the red laser light 516 or blue laser
light 517 emitted respectively from the green laser light source 501 and
the red laser light source 502 or blue laser light source 503 go through
the illumination optical systems 504a and 504b corresponding to the green
laser light 515 and the red laser light 516 or blue laser light 517, and
enters the prism 510 by way of the light guide prism 514. Then the green
laser light 515 and the red or blue laser light 516 or 517 transmit
themselves in the prism 510, and enters the package 511, which is joined,
to the bottom of the prism 510.

[0293]Then, having passed the package 511, the green laser light 515 and
the red or blue laser lights 516 or 517 enter the two mirror devices 520
and 530 which are housed in a single package 511 and which correspond to
the individual laser lights 515, 516 and 517. Having been modulated at
the respective mirror devices 520 and 530, the individual laser lights
515, 516 and 517 are reflected to the inclined surface direction of the
prism 510.

[0294]The next is a description of the principle of projection starting
from the reflection of the individual laser lights 515, 516 and 517 at
the respective mirror devices 520 and 530 to the projection of an image
by referring to the rear view diagram of the two-plate projection
apparatus 500 shown in FIG. 15B.

[0295]FIG. 15B is a rear view diagram of a configuration of a two-plate
projection apparatus comprising two of a mirror device according to the
present embodiment.

[0296]A green laser ON light 518 and a red or blue laser ON light 519
reflected to the inclined surface direction of the prism 510 by means of
the respective mirror devices 520 and 530 in the ON state are
re-transmitted through the package 511, thus entering the prism 510.
Then, the green laser ON light 518 and the red or blue laser ON light 519
are respectively reflected on the inclined surface of the prism 510. Then
the green laser ON light 518 is re-reflected on the film 505 allowing a
passage of only a light of a specific wavelength while reflecting the
light of other wavelengths. Meanwhile, the red or blue laser ON light 519
is transmitted through the film 505. Then, the green laser ON light 518
and the red or blue laser ON light 519 are synthesized on the same
optical path and incident together to the projection optical system 523,
thereby projecting a color image. Note that the optical axes of the
respective ON lights 518 and 519 emitted to the projection optical system
523 from the prism 510 are preferably to be perpendicular to the emission
surface of the prism 510.

[0297]Therefore, the configuration as described above enables a projection
of image by using the two-plate projection apparatus 500 comprising two
of the mirror device described above.

[0298]FIG. 15C is a side view diagram of a configuration of a two-plate
projection apparatus comprising two of the mirror device described above.

[0299]The green laser light 515 emitted from the green laser light source
501 enters the light guide prism 514 perpendicularly by way of the
illumination optical system 504a. Having been transmitted through the
light guide prism 514, the green laser light 515 transmits itself through
the prism 510 joined with the light guide prism 514 and enters the mirror
array 521 of the mirror device 520 housed in the package 511.

[0300]The mirror array 521 reflects the incident green laser light 515 by
the deflection angles of the mirror in either of the ON state in which
the entire reflection light enters the projection optical system 523, of
the intermediate light state in which a portion of the reflection light
enters the projection optical system 523 or of the OFF light state in
which none of the reflection light enters the projection optical system
523. A green laser light 524 selecting the ON light state is reflected on
the mirror array 521, and thus the entire light enters the projection
optical system 523.

[0301]Meanwhile, a laser light 525 selecting the intermediate state is
reflected on the mirror array 521, and thus a portion of the light enters
the projection optical system 523. And a laser light 526 selecting the
OFF light is reflected by the mirror array 521 toward the light shield
layer 513 featured on the back surface of the prism 510. And the
reflected laser light 526 is absorbed in a light shield layer 513. By
this, the green laser lights by the ON light in the maximum quantity of
light, by the intermediate light in the intermediate quantity of light
between the ON light and OFF light, or by the OFF light in the zero
quantity of light are incident to the projection optical system 523. Note
that the making of the deflection angle of the mirror stay between the ON
light state and OFF light state makes it possible to create an
intermediate light state. And the making of the mirror in a free
oscillation as described above repeats the deflection angles of the
mirror at a deflection angle constituting the ON state, at the angle
constituting the intermediate state and at the angle constituting the OFF
state. Here, a control of the number of free oscillations makes it
possible to adjust a quantity of light incident to the projection optical
system 523. As such, the generation of a quantity of light in the
intermediate state enables the projection of an image with a high grade
of gray scale.

[0302]It is possible to carry out a similar process on the reverse
surface, that is, on the side having the red laser light source 502 and
blue laser light source 503.

[0303]FIG. 15D is a plain view diagram of a two-plate projection apparatus
comprising two of a mirror device according to the present embodiment.

[0304]The light of an OFF light state can be absorbed by the light shield
layer 513 on the back without being reflected on the inclined surface of
the prism 510 by placing the individual mirror devices 520 and 530 so as
to be 45 degrees in relation to the four sides of the outer circumference
of the package 511 on the same horizontal plane as shown in FIG. 15D.

<Three-Plate Projection Apparatus>

[0305]The next is a description on a three-plate projection apparatus.

[0306]The three-plate projection apparatus makes three mirror devices
respond to the respective lights of three groups of light sources and
makes the individual mirror devices modulate the individual lights from
the respective light sources. Then the individual lights modulated by the
respective mirror devices are synthesized for projecting an image.

[0307]As an example, when projecting an image by the lights of three
colors, i.e., red light, green light and blue light, the individual
lights are continuously modulated by the respective mirror devices and
the modulated individual lights are synthesized, thereby projecting a
color image.

[0308]FIG. 16 is a configuration diagram of a three-plate projection
apparatus comprising three of a mirror device, according to the present
embodiment, housed in the respective packages.

[0310]The next is a description of constituent members of the projection
apparatus 600 shown in FIG. 16.

[0311]The light source 601 may be a mercury lamp source, a laser light
source, an LED, or such, likewise the light source described for the
single-plate projection apparatus and two-plate projection apparatus
describe above. The configuration and operation of the light source, such
as the sub-light source and/or pulse emission, are similar to the light
source for the projection apparatus described above and therefore the
description is omitted here.

[0312]The condenser lens-1 602, rod integrator 603, condenser lens-2 604
and condenser lens-3 605 are similar to those described for the single
plate projection apparatus and the condenser lens-1 602, condenser lens-2
604 and condenser lens-3 605 have the role of focusing the light.
Meanwhile, the rod integrator 603 has the role of evening out a light
intensity.

[0313]The TIR prism 608 is similar to the prism described for the
single-plate projection apparatus described above and therefore the
description is omitted here. Note that the TIR prism 608 used for the
three-plate projection apparatus shown in FIG. 16 is constituted by a
first prism 606 and a second prism 607.

[0314]The first dichroic prism 609 and second dichroic prism 610 are
prisms letting only the light of a specific wavelength pass while
reflecting the light of other wavelengths. And the third prism 611 is a
common prism. Note that the first dichroic prism 609 and second dichroic
prism 610 may be configured by respective dichroic mirrors.

[0315]As an example, FIG. 16 shows the case of configuring the first
dichroic prism 609 as a prism reflecting only the light of the wavelength
equivalent to red while letting the light of other wavelengths pass and
the second dichroic prism 610 as one reflecting only the light of the
wavelength equivalent to blue while letting the light of other
wavelengths pass. And the drawing shows the case of configuring the third
prism 611 as one making the light of the wavelength equivalent to green
travel straight.

[0316]The individual packages 615, 616 and 617 house the respective mirror
devices 612, 613 and 614 according to the present embodiment.

[0317]The projection lens 618 has the role of enlarging individual lights
synthesized after the individual lights are reflected and modulated at
the respective mirror devices 612, 613 and 614.

[0318]A processor 620 is basically similar to the one described for the
single plate projection apparatus, and comprises a spatial light
modulator control unit 621 and a light source control unit 622. And it
processes the input image signal data as described for the single plate
projection apparatus.

[0319]The spatial light modulator control unit 621, being basically
similar to the one described for the single plate projection apparatus,
is connected to the individual mirror devices 612, 613 and 614. And it is
capable of controlling the individual mirror devices 612, 613 and 614
either independently or synchronously based on the image signal data
processed by the processor. It is also capable of controlling the
individual mirror devices 612, 613 and 614 synchronously with other
constituent members.

[0320]The light source control unit 622, being similar to the one
described for the single plate projection apparatus, is connected to the
light source 601 and capable of controlling the light intensity of the
light source, the number of sub-light sources to be lit and such based on
the image signal processed by the processor. Frame memory 623 and an
image signal input unit 624 are similar to the ones described for the
single plate projection apparatus and therefore the description is
omitted here. Such are the constituent members comprised by the
three-plate projection apparatus 600 shown in FIG. 16.

[0321]The next is a description of the principle of projection of a color
image at the three-plate projection apparatus 600 shown in FIG. 16.

[0322]In the three-plate projection apparatus 600, the light output from
the light source 601 is transmitted through condenser lens-1 602, rod
integrator 603, condenser lens-2 604, condenser lens-3 605 in sequence
and incident to the first prism 606 of the TIR prism 608 at a critical
angle or more. Then, the incident light is totally reflected by the first
prism 606 of the TIR prism 608. The totally reflected light enters the
first dichroic prism 609. And only the light of the wavelength equivalent
to red, among the totally reflected light, is reflected, while the light
of other wavelengths are passed, on the emission surface for light of the
first dichroic prism 609 and/or on the incident surface for light of the
second dichroic prism 610. Then, as for the light incident to the second
dichroic prism 610, only the light of the wavelength equivalent to blue,
among the incident light, is reflected, while the light of other
wavelength, that is, the light equivalent to green, is passed on the
light emission surface of the second dichroic prism 610 and/or the light
incident surface of the third prism 611.

[0323]The light from which the light of wavelengths equivalent to blue and
red are removed which enters the third prism 611, that is, the light
equivalent to green travels straight in the third prism 611. Then, the
light dispersed to each wavelength is incident to the packages 615, 616
and 617, respectively, which house the respective mirror devices 612, 613
and 614 that are placed on the respective sides of the first dichroic
prism 609, second dichroic prism 610 and third prism 611.

[0324]The individual lights transmitted through the packages 615, 616 and
617 enter the respective mirror devices 612, 613 and 614 according to the
present embodiment. Here, the individual mirror devices 612, 613 and 614
are mutually independently controlled by the spatial light modulator
control unit 621 so as to respond to the respective lights based on the
image signal processed by the processor 620. The individual mirror
devices 612, 613 and 614 modulate, and reflect, the incident respective
lights. Then, the light equivalent to the wavelength of red, reflected by
the mirror device 612, re-enters the first dichroic prism 609. Also, the
light equivalent to the wavelength of blue, reflected by the mirror
device 614, re-enters the second dichroic prism 610. And the light
equivalent to the wavelength of green, reflected by the mirror device 613
re-enters the third prism 611.

[0325]The light equivalent to the wavelength of red, re-entering the first
dichroic prism 609, and the light equivalent to the wavelength of blue,
re-entering the second dichroic prism 610, repeat some numbers of
reflections in the respective prisms 609 and 610. Then, the light
equivalent to the wavelength of blue overlaps its optical path with that
of the light equivalent to the wavelength of green, re-entering the
second dichroic prism 610 from the third prism 611, thereby being
synthesized. Then, the light synthesized with the wavelengths equivalent
to green and blue enters the first dichroic prism 609 from the second
dichroic prism 610. Then, the light equivalent to the wavelength of red
overlaps its optical path with that of the light equivalent to the
wavelengths of green and blue, entering the first dichroic prism 609 from
the second dichroic prism 610, thereby being synthesized.

[0326]The light of a result of synthesizing the individual lights
modulated by the respective mirror devices 612, 613 and 614 enters the
second prism 607 of the TIR prism 608 at the angle smaller than the
critical angle.

[0327]Then, the synthesized light is transmitted through the second prism
607 of the TIR prism 608 and is projected to the screen 619 by way of the
projection lens 618. As such, a color image can be projected at the
three-plate projection apparatus.

[0328]In such a configuration, as compared to the single-plate image
display system described above, since each light of the primary colors is
displayed at all times, there will be no visual problem such as the
so-called color breakup. Furthermore, an effective use of the emitted
light from the light source provides in principle a bright image. Such is
a description of a projection apparatus comprising a mirror device(s)
according to the present embodiment.

[0329]As such, the present specification document has described the mirror
device comprising a plurality of electrodes equipped on a substrate, a
hinge connected to at least one of the electrodes, a mirror connected to
the hinge and corresponding to at least one of the electrodes, in which a
barrier layer is comprised between the hinge and mirror, and/or between
the hinge and electrode. Also noted is the mirror device production
method for producing such-configured mirror device. Further noted is the
projection apparatus comprising such-configured mirror device.

[0330]Various alternations and modifications have no doubt become apparent
to those skilled in the art after reading the above disclosure.
Accordingly, it is intended that the appended claims be interpreted as
covering all alternations and modifications as falling within the spirit
and scope of the invention. Although the present invention has been
described by exemplifying the presently preferred embodiments, it shall
be understood that such disclosure is not to be interpreted as limiting.
Various alternations and modifications will no doubt become apparent to
those skilled in the art after reading the above disclosure. Accordingly,
it is intended that the appended claims be interpreted as covering all
alternations and modifications as falling within the true spirit and
scope of the invention.